For some reason this is my favorite stat.
I estimate team "luck" by using my efficiency regression model to calculate each team's expected wins--how many wins a team can normally expect, on average, given their actual performance in offensive and defensive running, passing, turnovers, and penalties. The difference between the expected wins and actual wins is what I loosely call team luck.
What do I mean by luck?
In my own life, I'm a big believer in hard work, preparation, focus, execution and everything else that isn't luck. Coaches and players can't let themselves think any other way for a single second. But once we account for all those things, what do we call what's left over? Statisticians call it "residual," and a substantial portion of any residual is due to random effect, including sample error and what I call "bunching." In a bounded and meticulously measured system like sports, a vast amount of the residual from any decent model will be due to randomness. A season of 16 games simply isn't long enough for the breaks to even out.
There are plenty of things my model does not consider, special teams being the most prominent. But special teams plays are the most random events in the sport, save for the coin flip. Luck is a punt that lands on the 5 and skids into the end zone for touchback instead of bouncing into the air and being downed at the 1. A kick or punt return for a touchdown certainly requires skill, but when the kick return (or missed field goal or anything else) occurs means everything.
A missed FG when a team is already ahead by 20 points doesn't mean much, but when a team is behind by 1 in the 4th quarter, it means the game. Teams and players can't control when those events occur, or else they'd save up their successes for when they matter most and their failures for when they don't. So in a very substantial way, they are luck, at least when it comes to deciding game outcomes. (For a more thorough discussion, see this post.)
Schedule strength is part of luck too. Teams fortunate enough to have a soft schedule (so far) are likely to have more wins than a team unlucky enough to face a tougher schedule. Even though schedule strength is something real that can be measured, it still lies outside of a team's control.
2009's Lucky and Unlucky Teams So Far
The luckiest teams so far this year include the Vikings, Colts, Bengals, and Saints. Usually when teams have extremely good records, they are both good and lucky. The reason is simple: It's extremely rare for a team to have a good record and at the same time be unlucky.
One tangible example of what I'm talking about was on display at the end of regulation in the Saints-Redskins game. Kickers miss short field goals periodically, but they usually go unnoticed unless it costs the game. (Now former) Redskins kicker Sean Suisham missed a chip-shot FG that would have put his team up by 10 points and iced the victory. Instead, Suisham missed and New Orleans was able to drive 80 yards for a TD to send the game to OT. The Saints were both lucky and good.
On the other side of the coin are the Redskins (unsurprisingly), Steelers, Buccaneers and Rams, who have received the short end of the stick more than their fair share this year.
The Charmed One (Part 2)
Two years ago the Brett Favre-led Packers topped this list as the luckiest team. At the time, my Packer-fan brother-in-law astutely observed that my model was not measuring luck. Rather, it was measuring "Favre-ness." Then last year, the Favre-led Jets topped this list going into the final games of the season, while the Favre-less Packers became the unluckiest team.
Guess which team tops the list this season. The Favre-led Minnesota Vikings are the luckiest so far in 2009, with 2.7 more wins than we'd expect given their general on-field performance. This is not a knock against Favre. In fact, my Win Probability Added (WPA) analysis put him at the top of the MVP list as the player who has contributed most to his team's success. Maybe my brother-in-law is right.
Then again, maybe it has more to do with missed last-second field goals, a weak schedule, and some good old-fashioned luck. In terms of efficiency (yards per play), the Vikings don't look that great on paper. On offense they are 9th in pass efficiency, 18th in run efficiency, 14th in fumble rate, and 1st in interception rate. On defense they are 13th against the pass, 10th against the run, and 26th in interception rate. Overall, they are 13th in the league in penalty yards per play. Yet the gods of football are smiling on the Metrodome, blessing the Vikes with the third best record in the NFL at 10-2.
Here is the full list. Click on the headers to sort.
|RANK||TEAM||GWP||Expected W||Actual W||Luck|