Special Note

Advanced NFL Stats is now Advanced Football Analytics. Sorry for the inconvenience and broken links, but the change was long overdue. Although the old address forwards here, you'll likely need to to update your RSS subscription and bookmarks.

Sneak Peak at WP 2.0

I've just completed the development, validation, and testing of the next-generation Win Probability model. It took the better part of the past 6 months. Despite many heartaches and frustrating turns, I'm really thrilled with the results. But as excited as I am to have this new tool, I'm also somewhat humbled by how inadequate the original model is in some regards.

As a quick refresher the WP model tells us the chance that a team will win a game in progress as a function of the game state--score, time, down, distance...etc. Although it's certainly interesting to have a good idea of how likely your favorite team is to win, the model's usefulness goes far beyond that.

WP is the ultimate measure of utility in football. As Herm once reminded us all, You play to win the game! Hello!, and WP measures how close or far you are from that single-minded goal. Its elegance lies in its perfectly linear proportions. Having a 40% chance at winning is exactly twice as good as having a 20% chance at winning, and an 80% chance is twice as good as 40%. You get the idea.

That feature allows analysts to use the model as a decision support tool. Simply put, any decision can be assessed on the following basis: Do the thing that gives you the best chance of winning. That's hardly controversial. The tough part is figuring out what the relevant chances of winning are for the decision-maker's various options, and that's what the WP model does. Thankfully, once the model is created, only fifth grade arithmetic is required for some very practical applications of interest to team decision-makers and to fans alike.

Podcast Episode 26 - Keith Goldner

Keith Goldner, AFA contributor and Chief Analyst at Numberfire, returns to provide some fantasy football wisdom. He dissects the different strategies for snake, auction and keeper league drafts, and explains how to incorporate risk management strategies when creating your roster. Keith and Dave also touch on daily fantasy games, and look at how to craft the optimal lineups for various league types. They close out the episode by highlighting the players to watch during the 2014 fantasy season.

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Podcast Episode 25 - Aaron Schatz

Aaron Schatz, founder of Football Outsiders, joins the podcast to discuss the newly released 2014 Football Outsiders Almanac. Aaron explains how he and his team developed a system to combine game film analysis with box score data to create their own advanced metrics.  He breaks down the difference between rate statistics and totals, and explains how the concept of “replacement level” is important in football. Aaron also provides team-by-team breakdowns and predictions, and finishes up the episode by conquering Dave’s “lightning round” of questions.

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Implications of a 33-Yard XP

The NFL is experimenting with a longer XP this preseason. XPs have become so automatic (close to 99.5%) that there no longer much rationale for including them in the game. The Competition Committee's experiment is to move the line of scrimmage of each XP to the 15-yard line, making the distance of each kick 33-yards.

Over the past five seasons, attempts from that distance are successful 91.5% of the time. That should put a bit of excitement and drama into XPs, especially late in close games, which is what the NFL wants. But it might also have another effect on the game.

Currently, two-point conversions are successful at just about half that rate, somewhere north of 45%. The actual rate is somewhat nebulous, because of how fakes and aborted kick attempts into two-point attempts are counted.

It's likely the NFL chose the 15-yd line for a reason. The success rates for kicks from that distance are approximately twice the success rate for a 2-point attempt, making the entire extra point process "risk-neutral." In other words, going for two gives teams have half the chance at twice the points.

Podcast Episode 24 - Brian Burke

Brian Burke returns to recap his busy summer offseason. After a brief lesson on the rules of Gaelic Football, Dave and Brian discuss what we can learn about NFL win shares from Jimmy Graham’s contract, some new updates to the site (WOPR, and Win Probability Model) and the 2014 season predictions Brian made for ESPN the magazine. Dave also issues a call for podcast contributors, looking for anyone interested in contributing their technical expertise to the show.

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Win Values for the NFL

Jimmy Graham's contract values him at about 0.9 wins per season. Here's how I came to that estimate.

In 2013 the combined 32 NFL teams chased 256 regular season wins and spent $3.92 billion on player salary along the way. In simple terms, that would make the value of a win about $15 million. Unfortunately, things aren't so simple. To estimate the true relationship between salary and winning, we need to focus on wins above replacement.

Think of replacement level as the "intercept" term or constant in a regression. As a simple example think of the relationship between Celsius and Fahrenheit. There is a perfectly linear relationship between the two scales. To convert from deg C to deg F, multiply the Celsius temperature by 9/5. That's the slope or coefficient of the relationship. But because the zero point on the Celsius scale is 32 on the Fahrenheit scale, we need to add 32 when converting. That's the intercept. 32 degrees F is like the replacement level temperature.

No matter how teams spend their available salary, they need to have 53 guys on their roster. At a bare minimum, they need to spend 53 * $min salary just to open the season. We can consider that amount analogous to the 32-degrees of Fahrenheit. For 2013, the minimum salaries ranged from $420k for rookies to $940k for 10-year veterans. To field a purely replacement level squad, a franchise could enlist nothing but rookies. But to add a bit of realism, let's throw in a good number of 1, 2, and 3-year veterans in the mix for a weighted average min salary of $500k per year. The league-wide total of potential replacement salary comes to:

Sun Tzu on Analytics

Apparently he was a fan:

Now the general who wins a battle makes many calculations in his temple ere the battle is fought. The general who loses a battle makes but few calculations beforehand. Thus do many calculations lead to victory, and few calculations to defeat: how much more no calculation at all! It is by attention to this point that I can foresee who is likely to win or lose.
For those of you who may be unfamiliar with Sun Tzu, he was the ancient Chinese general and philosopher who wrote The Art of War. Still required reading around military academies and war colleges around the world to this day, The Art of War is perhaps the most influential military treatise in history. It crystallizes centuries of strategic wisdom into what are essentially tweet-sized chunks of timeless insight. Thus do many calculations lead to victory...I like that part. I think I'm gonna' put it on a t-shirt.

Podcast Episode 23 - John Urschel

John Urschel, professional football player and mathematician, joins the show. John was recently selected in the 5th round by the Baltimore Ravens in this year's NFL draft. Last season, John was a Penn State football co-captain and as a student-athlete he achieved a 4.0 GPA while majoring in math. For his efforts, he won the Campbell Trophy, awarded to the top scholar athlete in Division one football. He recently proved the Urschel-Zikatanov Generalized Bisection Theorem and published his findings in the Journal of Celestial Mechanics and Dynamical Astronomy.

On the show, John explains how he came to love the world of mathematics, and how his passion for football aligns with his commitment to academics. He also shares some of the lessons he's learned from veterans in OTAs and describes how he's preparing for the upcoming NFL season.

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