Big Changes Coming

I'm preparing to move the site to a new platform. Within a day or so the site will be hosted on a new content management system, which will allow us much more flexibility with all the new tools and content coming this season. I'm not sure how smooth the transition will be, so please stay tuned via Twitter in case things get broken over the next couple days.

With the url  (web address) change earlier this year and now this change, I've completely destroyed the site's search rankings (which were really good), links, and 7 years of goodwill. I apologize.

To fix things, I'll need your help. Please update your links to the site's url and, more importantly, spread the word. Hopefully you've enjoyed reading the posts or using the other features at AFA over the past several years. I haven't asked much in return, so please give the site a shout out on Twitter, your own site, or whatever platform you have.

Just to be perfectly clear, here are how things are changing:

1. The new site will offer all the same content you've come to expect, including analysis, tools, live WP graphs, advanced stats, the podcast, advanced boxscores, and visualizations. In addition, it will have a separate section for team clients and media outlets who use AFA services.

2. The web address will continue to be

3. The twitter handle will remain @Adv_NFL_Stats.

4. The site's feed will change to  (or ...&type=atom, depending on your preference.)

5. The podcast feed will continue to be

6. For now, older content will continue to be hosted at

For the month of October I'll be celebrating the re-launch of the site with a feature of the day, highlighting many of the most popular things the site has to offer.

Biggest Plays of the Week

In case you miss the links I send out on Twitter, Deadspin's sub-site Regressing is running a series on the biggest plays of the week. I created a tool for them them lists the biggest plays in terms of Win Probability Added (WPA).

Reading the comments, people seem to take delight in the negative plays for whatever reason. Cutler's interceptions appear to invite a lot of anti-fans. There's also loyal fans who like to pile on the misfortunes of their own team out of frustration. I can see that this week with E.J. Manuel's bad day yesterday.

But keep in mind a "negative" play is all in the perspective. A bad play to an offense is a great play to a defense. Statistically, there is no good and bad. Manuel's interception to Watt was both a poor by play by a quarterback and an alert and athletic play by a defensive lineman.

If and when Regressing gets tired of posting these, I'll make the tool public so you can look up the most agonizing moments in your hometown team's season anytime you want.

Sunday's Numbers Have Been Crunched

Sunday's numbers are now available, including advanced stat box scores, top players of the week, team stats, and season leader boards.

Team Advanced Stats Viz
Position Leaders Viz
Advanced stat box scores
Top QBs of the week
Top RBs of the week
Top WRs of the week
Top TEs of the week
Top Defenders of the week
Advanced team stats
Offensive player season leaders
Defender season leaders
QB Viz
RB Viz

Chip's Challenging Decisions

The Eagles lost to the 49ers on Sunday 26-21 in what essentially came down to two plays by the Eagles on 3rd and 4th-and-Goal from just outside the 1-yard line. There is no denying it was a close game - even though the Eagles offense was unable to move the ball all day. The Eagles made a few interesting decisions - or lack of decisions - in the second half including not challenging a 3rd-down conversion reception and accepting a penalty on 3rd-and-3 after an incompletion. Let's examine each and see how they could have affected the Eagles' win probability, keeping in mind that in close games, every percentage point counts.

Throw The Red Flag

With 2:09 left in the 3rd quarter, winning 23-21, San Francisco faced a 3rd-and-9 from their own 27. Colin Kaepernick dropped back and hooked up with Anquan Boldin for a 12-yard completion. It appeared Boldin bobbled the ball and potentially trapped it on the completion. In today's game where most of the biggest plays are automatically reviewed (scoring plays and turnovers), a long 3rd-down conversion in a close game is one of the higher leverage challenge situations.

One Thing I Learned from the WOPR

How can TB upset PIT? How does MIN overwhelm ATL with a rookie QB? How did the NYG offense suddenly break out with 45 points? How does DAL embarrass NO on both sides of the ball?

The WOPR is my game simulation engine. I've had a ton of fun experimenting with different things, finding out when teams should make various tactical decisions that might be uncommon or hard to isolate empirically (directly from the data). But one of the more profound things I learned from the WOPR relates to game outcomes between completely even teams.

Weekly Game Probabilities - Week 4

Weekly game probabilities for week 4 are now up at Sports on Earth. Probabilities are a blend of the pre-season team strength estimates with a strong dose of stats from weeks 1, 2 and 3.

Please remember that the projected scores are not to be taken terribly seriously. Do not bet the mortgage on them as they are not intended to graded against the spread. They are simply a "maximum-plausibility" estimate given respective team scoring tendencies.

Team Efficiency Rankings: Week 3

The return of the team efficiency rankings comes with some important changes for 2014.  As most of you know, Brian revamped the win probability model for this year to provide more precise estimates in a greater variety of contexts.

This obviously holds big implications for the rankings, which are based on the generic win probability (GWP) of a particular team against an average team.  But more importantly, both are predictive models which emphasize factors that best suggest how likely a team is to fare in the future.  When one improves, the other should theoretically improve alongside it.

We'll keep an eye on that hypothesis as the season moves along.  Perhaps I'll write something at the end of the season comparing the accuracy of this year's model to 2013's.  For now, let's take a look at some of the most notable trends from the first rankings of 2014 (click here for a full explanation of the rankings methodology).

Leaving Free WP All Over the Field

If you were a coach, would you voluntarily give up a down at some point in the game, just to be sporting? Ehh, let's just make it 3rd and 5 instead of 2nd and 5. Of course not. For a random play in the 2nd quarter, that would cost you about 0.02 WP (2% chance of winning) for no reason.

So why do NFL coaches voluntarily leave WP out on the field?

Take yesterday's DEN-SEA game as an example. SEA was ahead 17-12 in the 4th quarter, and had the ball deep in their own territory with about 9 minutes to play. With the game clock running, they snapped the ball with: 8, 5, 5, 8, and 10 seconds left on the play clock. That's a total of 36 seconds. Plus, there was a play in which the receiver could have just as easily remained in bounds. Because there was more than 5 minutes left in the game and the clock restarts after the ball is set, that may have only cost 10-15 seconds of play clock rather than up to 40 seconds. To be fair let's say there was a total of 46 seconds SEA could have burned off the clock during their second to last drive with almost no effort or risk.

Sunday's Numbers Have Been Crunched

Sunday's numbers are now available, including advanced stat box scores, top players of the week, team stats, and season leader boards.

Team Advanced Stats Viz
Position Leaders Viz
Advanced stat box scores
Top QBs of the week
Top RBs of the week
Top WRs of the week
Top TEs of the week
Top Defenders of the week
Advanced team stats
Offensive player season leaders
Defender season leaders
QB Viz
RB Viz

Texans Try Once, Fail Twice

Down 14-0 at the start of the second half to the New York Giants,
the Houston Texans faced a 4th-and-1 on their own 46-yard line. At this point, with just a 9.0% chance to win, Bill O'Brien made the correct call to go for it. A successful conversion means a 12.9% win probability, while a punt means about an 8.6% chance to win. The break-even point going for it is far below an estimated 65% conversion rate on 4th-and-1. Alfred Blue ran off right tackle and was stuffed, turning the ball over on downs. The Giants would kick a field goal to go up 17-0.

On the very next drive, Ryan Fitzpatrick led the Texans downfield to the Giants 9-yard line where they faced another 4th-and-1. With 6:13 left in the third, down 17, Bill O'Brien elected to take the chip-shot field goal. Even the commentators suggested he should be going for it. Obviously, the prior failure on fourth down should not have an affect on the Texans' decision this time. If that were the case, O'Brien would be judging his previous decision on the outcome, rather than the process. The only other logic could be that he figured they would need a field goal at some point, down 17 - common faulty logic in the NFL as coaches should be doing whatever they can to maximize their chances of winning.

Eagles-Colts Call on MNF: Not Actually That Important

By Kurt Bullard
Kurt is a sophomore at Harvard and a second-year member of the Harvard Sports Analysis Collective. He intends to major in either Economics or Statistics. Go 'Cuse.

Football fans – and sports fans in general – abhor the fact that mistakes made by the referees at the end of games can influence the result of the contest. Nowhere was this seemingly more apparent than in this week’s Monday Night Football game. Indianapolis seemed to have the game all but wrapped up towards the end of the fourth quarter. With a 27-20 lead and the ball at the Eagles 22 with 5:15 remaining, the Colts seemed poised to score – either by capping off the drive with a touchdown or settling for a field goal behind the reliable leg of Adam Vinatieri. However, on a 3rd and 9 call, Luck dropped back and targeted T.Y. Hilton, but was intercepted by Malcolm Jenkins, injecting the Eagles with what seemed to be a second life. The Eagles managed to score quickly to knot up the game behind the legs of Darren Sproles and would go on to win the game in regulation off the leg of Cody Parkey. However, this was all possible due to a missed pass interference call on Brandon Boykin, who held Hilton coming out of his break, allowing the ball to sail past Hilton and into the hands of Jenkins.

Weekly Game Probabilities

Weekly game probabilities for week 3 are now up at Sports on Earth. Probabilities are a blend of the pre-season team strength estimates with a moderate dose of stats from week 1 and 2.

Please remember that the projected scores are not to be taken terribly seriously. Do not bet the mortgage on them as they are not intended to graded against the spread. They are simply a "maximum-plausibility" estimate given respective team scoring tendencies.

Podcast Episode 29 - Brian Burke

Brian Burke makes his first regular season appearance on the podcast to recap week two and discuss his latest research. Brian explains his break-even models for two point conversions and challenges and describes how the WOPR allows him to create test data for all sorts of interesting hypothetical game strategies. He also discusses an upcoming post that examines when teams should start running their "four minute offense". Dave and Brian close out the episode with an update on the 4th down bot and the new home and format for Brian's weekly game predictions.

This episode is sponsored by DraftKings, the leading provider of daily fantasy sports. If you use this link or promo code "AFA" to create a new account and make a deposit you'll gain a free $2 entry into this weekend's $100,000 Play Action Tournament.

Subscribe on iTunes and Stitcher

Two-Point Conversion in the KC-DEN game

With 7:15 left in the 4th quarter against DEN, KC's Knile Davis ran for a 4-yard TD, narrowing the Broncos' lead 21-16 pending the extra point or two-point conversion. Andy Reid elected for the extra point, and following the kick the Chiefs trailed by 4 points rather than 3 or 5 points resulting from a two-point try.

NFL coaches typically adhere to what's known as the Vermeil Chart for making two-point decisions. The chart was created by Dick Vermeil when he was offensive coordinator for UCLA over 40 years ago. It's a very simple chart that simply looks at score difference prior to any conversion attempt and does not consider time remaining, with one caveat. It applies only when the coach expects there to be three or fewer (meaningful) possessions left in the game.

With just over 7 minutes to play, there could be three possessions at most left, especially considering that at least one of those possessions would need to be a KC scoring drive for any of this to matter. (In actuality, there were only two possessions left, one for each team.) Even the tried-and-true Vermeil chart says go for two when trailing by 5. But it's not the 1970s any more and this isn't college ball, so let's apply the numbers and create a better way of analyzing go-for-two decisions.

Except for rare exceptions I've resisted analyzing two-point conversion decisions with the Win Probability model because, as will become apparent, the analysis is particularly susceptible to noise. Now that we've got the new model, noise is extremely low, and I'm confident the model is more than up to the task.

First, let's walk through the possibilities for KC intuitively. If KC fails to score again or DEN gets a TD, none of this matters. Otherwise:

Chiefs Crawling Drive, Come Away With Nothing

The Chiefs lost to the Broncos 24-17 on Sunday and had a chance to at least tie the game at the very end. Kansas City kept Peyton Manning off the field for an enormous chunk of the second half. The Broncos offense had only two drives after halftime (not including the final kneel down), one for a punt, one for a field goal, totaling just 8:51 in possession. The longest drive came from the Chiefs at the very start of the second half, where they ran 23 plays, taking 10 minutes off the clock... and ultimately missed a field goal. This got me thinking, how does drive length (in minutes) affect the probability of a team scoring?

First, here's a look at the ridiculous drive using our Markov model:

SOE: Weekly Game Probabilities

Weekly game probabilities for week 2 are now up at Sports on Earth. Probabilities are a combination of the pre-season team strength estimates with a small dose of stats from week 1.

Nick Foles and Interception Index Regression

Nick Foles and Josh McCown were two of last season's most pleasant surprises, emerging from obscurity to post two of league's most efficient seasons.  Both finished in the top 3 for Expected Points Added per Play, largely in part because the two combined to throw just three interceptions.

With one week of the 2014 season in the books,  Foles and McCown have already matched that combined total.  While everyone should have expected both to regress from their remarkably turnover-free 2013 seasons, that does not tell us how far each should regress based on historical norms.

Podcast Episode 28 - Chase Stuart

Chase Stuart rejoins the show to break down the surprising week one winners and losers. Chase shares his observations from the Jets home opener and explains some of the weekend's more intriguing game scripts. He also examines the data on exactly how important week one results are in predicting the season while looking ahead to the most intriguing week two match-ups.

Subscribe on iTunes and Stitcher

Simulating the Saints-Falcons Endgame

I was asked yesterday about the end of regulation of the Saints-Falcons game. With about a minute and a half remaining, NO was down by 4 but had a 1st & goal at the 1. With 2 timeouts left, should ATL have allowed the touchdown intentionally?

I previously examined intentional touchdown scenarios, but only considered situations when the offense was within 3 points. In this case NO needed a TD, which--needless to say--makes a big difference. Yet, because NO was on the 1, perhaps the go-ahead score was so likely that ATL would be better off down 3 with the ball than up 4 backed-up against their goal line.

This is a really, really hard analysis. There's a lot of what-ifs: What if NO scores on 1st down anyway? What if they don't score on 1st but on 2nd down? On 3rd down? On 4th down? Or what if they throw the ball? What if they stop the clock somehow, or commit a penalty? How likely is a turnover on each successive down? You can see that the situation quickly becomes an almost intractable problem without excessive assumptions.

That's where the WOPR comes in. The WOPR is the new game simulation model created this past off-season, designed and calibrated specifically for in-game analytics. It simulates a game from any starting point, play by play, yard by yard, and second by second. Play outcomes are randomly drawn from empirical distributions of actual plays that occurred in similar circumstances.

If you're not familiar with how simulation models work, you're probably wondering So what? Dude, I can put my Madden on auto-play and do the same thing. Who cares who wins a dumb make-believe game? 

Analyzing Replay Challenges

The new WP model allows some nifty new applications. One of the more notable improvements is the consideration of timeouts. That, together with enhanced accuracy and precision allow us to analyze replay challenge decisions. Here at AFA, we've tinkered with replay analysis before, and we've estimated the implicit value of a timeout based on how and when coaches challenge plays. But without a way to directly measure the value of a timeout the analysis was only an exercise.

Most challenges are now replay assistant challenges--the automatic reviews for all scores and turnovers, plus particular plays inside two minutes of each half. Still, there are plenty of opportunities for coaches to challenge a call each week.

The cost of a challenge is two-fold. First, the coach (probably) loses one of his two challenges for the game. (He can recover one if he wins both challenges in a game.) Second, an unsuccessful challenge results in a charged timeout. The value of the first cost would be very hard to estimate, but thankfully the event that a coach runs out of challenges AND needs to use a third is exceptionally rare. I can't find even a single example since the automatic replay rules went into effect.

So I'm going to set that consideration aside for now. In the future, I may try to put a value on it, particularly if a coach had already used one challenge. But even then it would be very small and would diminish to zero as the game progresses toward its final 2 minutes. In any case, all the coaches challenges from this week were first challenges, and none represented the final team timeout, so we're in safe waters for now.

Every replay situation is unique. We can't quantify the probability that a particular play will be overturned statistically, but we can determine the breakeven probability of success for a challenge to be worthwhile for any situation. If a coach believes the chance of overturning the call is above the breakeven level, he should challenge. Below the breakeven level, he should hold onto his red flag.

Eagles Escape Embarrassment

Let my bias not be unknown, I am an Eagles fan. Watching Nick Foles fumble twice, throw an interception, and Chad Henne connect with rookie Allen Hurns twice for touchdowns -- all in the first half -- was one of the more frustrating ways to start the season. The Eagles were lucky to only be down 17-0 at halftime. On the opening drive of the second half, Philly converted twice and Nick Foles connected with Darren Sproles for eight yards on 3rd-and-9, bringing up a 4th-and-1 at the Jaguars 49-yard line.

Chip Kelly is known for his progressive thinking and he didn't hesitate -- calling for a hurry-up, one of the first times the Eagles really played up-tempo in the game. The Jaguars safeties got crossed and a huge gap opened up as Darren Sproles ran untouched for a 49-yard score. The Eagles would not look back and ultimately went on to win "handily," 34-17. Had the Eagles not converted, though, Kelly would likely have been ridiculed for his call as it could have effectively ended the game (dropping Philly's win probability to 5.4%).

Let's look at the fourth down call, taking into consideration the relative strength of the two teams.

Weekly Game Probabilities: A New Home

This season the weekly game probabilities will be featured at Sports on Earth. Each game will have the probability, a score prediction, and a couple notes on why the numbers are what they are. In the early weeks of the season, the numbers are at least partially based on the same preseason estimates of team strength I used for the season projections. But as we get a few weeks of data, those preseason ratings will fade out.

For now the score predictions are simply maximum-plausibility estimates. (Yes, I just made that term up.) Predicting an actual score for each game is statistically boring. With few exceptions, a statistically sound estimate would be 24-20 or 27-21 for every game, so I've added some of the human element to the score predictions. The bottom line is that readers should focus on the probabilities and don't bet the mortgage on the scores.

The game probabilities will be matched up against the picks of Will Lietch, one of the cornerstone writers at SOE. The idea is to create a friendly competition between man and machine.

The game probabilities had a great run at the New York Times--5 years. But there are only so many thought-provoking or counter-intuitive lessons on probabilities and predictions that can be squeezed out of a week of NFL games. But AFA will continue working with the Times on various projects as the season unfolds.

Here's the link to the probabilities for week one. For those keeping score at home, I had the Seahawks at 66% to win last night.

The 4th Down Bot Returns

The 4th Down Bot is returning to the New York Times this season. You might recall we booted him up late last season, but this year he'll be around starting week one. At its heart, the bot is a fun application of the 4th Down Calculator feature here at AFA. It uses both the Expected Points model and the Win Probability model to estimate the best option for every 4th down as a game is in progress.

As I mentioned last year, although the 4th down issue is growing mold with smarter fans, it remains the lowest hanging fruit on the football analytics tree. So it's nice to be able to automate things and not have to do the analysis myself. But on the other hand, we can add 'football analyst' to the list of jobs being taken over by robots.

The Bot will be faster, more accurate, and come with some new features this season. Here is a brief introduction. Here's are a few notes on how it works. And here is his Twitter feed.

Season Projections Visualization

I put together a season projection visualization that illustrates the playoff probabilities and win totals for each team. The numbers are based on the results of the season prediction project I did for ESPN The Magazine.

The method used to create the projections is explained here.

The viz is intended one-stop shopping for the season outlook. The top window shows the probabilities each team will make the playoffs. Dark green indicates a playoff berth by winning the division, lighter green indicates a wildcard berth.

The three windows below are team-specific. Hover the cursor over (or tap) a team's column in the top chart to see its details below. The window on the left is a chart of win totals. The bars represent the probability the selected team will finish with a corresponding number of wins. The second window shows the same information presented in a different way. It's the cumulative probability of each win total. In other words, it's the probability the selected team will win at least that many games. The third window is a pie chart. (Yes, I know pie charts are the unloved orphans of the chart world.) It illustrates the probability each team will win its division.

2014 Season Predictions for ESPN the Magazine

ESPN asked me to predict the 2014  season for their NFL Preview edition of their magazine. I was very hesitant because predicting the season to any degree is extremely difficult. I'm even on record as proclaiming that all pre-season predictions are "worthless." (More on that below). "You want me to predict which teams make the playoffs?" "Yes," they said, "in fact, we want you to predict the winner of all 267 games."

Then it got worse. "We want you to predict every score of every game."

I started doing some math in my head. There's 267 games in the season, including the playoffs, which means there's 2^267 different possible combinations of game outcomes in the season. While that might sound like a lot of different possibilities, it's even more than a human being could possibly fathom. Physicists and astronomers estimate there are about 10^80 atoms in the universe (that's 100 quinvigintillion to you and me). And the NFL season's 2^267 possible outcomes comes to 2.4x10^80, or about 240 quinvigintillion. Put simply, there more than twice as many possible outcomes to the NFL season than there are atoms in the universe. And that just refers to wins and losses, and doesn't even consider scores.

So how hard could it be?