Accept or Decline: 1st & 5 vs 2nd & Short

Your team has just run the ball for a hard-fought 8-yard gain on 1st down bringing up a 2nd and 2. The defense was flagged for offsides giving you the option of making it 1st and 5. Should your team accept or decline the penalty or take the gain?

To simplify things, let’s only consider situations between the 20-yard lines. Looking at each option in terms of the probability of converting for a 1st down, you should be indifferent. Both situations convert equally as often at an 85% rate. But 1st down probability isn’t the whole story.

Another Run-Pass Balance Study

Benjamin Alamar, author of the Passing Premium paper (critiqued here), takes a second stab at comparing the values of running and passing with new research. A brief presenting his methodology and findings was presented at a recent symposium on sports statistics. This time Alamar uses expected points as a measure of value, and compares the EP values gained by passes with those of runs. He defines risk as the probability each play type will result in a negative EP change, and finds that running is both less productive and "riskier" than passing. There are three fairly big problems in the methodology. Fortunately, all three can be rectified.

First, Alamar creates his EP values using a simple linear regression (see slide 10). Using down, distance, and yardline (plus other variables controlling for quarter and other effects), he produces an EP equation. This is a really bad way to estimate EP values. They're not linear, and there are any number of interacting effects within. The Levitt-Kovash paper, in contrast, uses a regression with quintic terms and full interactions to create their EP values. (I prefer a  more direct method--looking at the data empirically and smoothing it using a method called LOESS.)

Roundup 11/8

A new site from the Harvard Sports Analysis Collective looks promising. (But what's with the term "Collective?" What happened to "Club?") Here they look at 2-point conversion decisions.  They also look at what effect the new wedge rule might be having on kickoff distances (not much, especially if you consider the weather is about to get a lot worse). Do teams with RB committees run better than teams with a feature back? How much more accurate are FG attempts when kicked indoors? Overall, the site asks some neat questions and is definitely headed in the right direction.

Greg Easterbrook on coaching: "One factor here is the Illusion of Coaching. We want to believe that coaches are super-ultra-masterminds in control of events, and coaches do not mind encouraging that belief. But coaching is a secondary force in sports; the athletes themselves are always more important. TMQ's immutable Law of 10 Percent holds that good coaching can improve a team by 10 percent, bad coaching can subtract from performance by 10 percent -- but the rest will always be on the players themselves, their athletic ability and level of devotion, plus luck."

I'd mostly agree with Easterbrook, however I'd say that a good coach can make a good team 10% better, but a bad coach can absolutely ruin a good team. In most cases though, the NFL rarely features coaches bad enough to do that kind of damage simply because the league is considered the top of its profession. I think the bigger point is that modern coaching, beyond the leadership aspect, is mostly about the illusion of control.

Game Probabilities - Week 9

Weekly game probabilities are available now at the nytimes.com Fifth Down. This week I also lead-in with break down of the Chargers-Giants matchup.

Efficiency Rankings - Week 9

The efficiency rankings are beginning to settle down approaching the midpoint of the season. Big movers include San Diego climbing from 8 to 5 and Arizona dropping like a rock from 11 to 19.

The Cards played poorly against a bad team, and most teams are tightly bunched around the league average. So it doesn't take much movement in GWP to drop a number of spots from the top to the bottom of the "pack."

There continues to be a correlation between opponent-adjusted team strength and strength-schedule. This indicates that the death of parity is greatly exaggerated. It seems that so far this year there have been a disproportionate number of games between the very best and very worst teams. Ironically, this may indicate parity is stronger than ever. The scheduling system is supposed to give the top teams two extra games against other division leaders, and the bottom teams two extra games against the other dwellers. If a dweller or two turns into an elite team, or if an elite team suddenly becomes a doormat, the current disparity is what we'd get. Besides, parity isn't just about keeping teams from having very good or very bad records in any one year. It's also about making sure they aren't the same teams year after year.

Team Offense Win Probability Added 2000-2008

Recently I looked at team defense through the lens of Win Probability Added (WPA). Every play changes a team's chances of winning, and we can sum all the ups and downs into a total WPA for any player, team, offense, or defense. In this post, I'll look at team offense.

As with defenses, one offense might be the best in yards and another might be the best in yards per play. Yet another offense might be the best in terms of points. WPA can cut through all that, and tell us which squads made the biggest impacts on winning.

WPA captures the things that other stats cannot. For example, consider an offense leading by one point with 3 minutes left in the game. A series of modestly successful runs to convert a first down and kill the clock won't make fantasy fans happy, but it effectively clinches the win. A stop and a punt would typically give the opponent over a 30% chance of winning, so that grinding first down conversion may mean more in terms of winning than almost any other series all season.

Team Defense Win Probability Added 2000-2008

We've seen how a win probability model can help coaches make better decisions, but it can also help settle some water cooler debates around the office. One of the cool things we can do with a win probability model is compare teams and players based based on how much they contribute to their chances of winning. If we sum up all the defense's contribution toward winning the game, we can truly rank defenses.

One team might have the best defense in terms of total yards, and another might have the best defense in terms of yards per play. Yet another might be the best in terms of points allowed. All of these ways of comparing defenses is flawed in one way or another. For example, a defense with a poor offense will be facing short fields frequently.

Win Probability Added (WPA) can account for these various considerations and provide a very good estimate of how good a squad actually was. WPA should be considered a 'narrative' stat. It measures what actually happened and doesn't attempt to any more than that.  I'll start by looking at defenses since 2000, as far back as my data goes.

An Open Letter to Dan Dierdorf

And to Brian Billick. And to all the other football analysts who use the word prideful. The Baltimore defense is not prideful. The Panthers offense is not prideful. I know you mean "full of pride," but there's already a word for that. It's called proud.

I realize that prideful has wormed its way into our lexicon, and now dictionaries even consider it a word, thanks primarily to your efforts. But please, what's wrong with just using proud?