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.
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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.
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.
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.
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.
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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:
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: