Monday, November 16, 2009

Belichick Made The Right Call

Photo by Keith Allison

Last night, near the end of an important game against the Indianapolis Colts in Week 10, the New England Patriots faced 4th-and-2 on their own 28-yard-line. The Patriots were ahead by 6 points, with 2 minutes and 8 seconds left on the clock. Conventional wisdom said the Patriots should punt the ball, to force Manning to try to drive the length of the field for a game-winning score. Instead, the Patriots went for it and failed to convert. The Colts went on to win.

Commentators are already arguing about whether Coach Belichick showed too little faith in his defense, or too much faith in his offense. It has nothing do with faith. It's all about giving your team the best chance of winning. And the numbers say that Belichick made the right call.

To assess whether Belichick chose wisely, I used Football Mogul to simulate the situation that the Patriots faced. Football Mogul had access to every detail of the game, including current rosters and playbooks for each team. It even takes into account the weather and wind, and the fatigue level of the New England defense.

Specifically, I simulated the remainder of the game exactly 20,000 times. For 10,000 of these simulations, the Patriots went for it on 4th-on-2. For the other 10,000 simulations, the Patriots punted.

We could look at this simply in terms of what chance the Colts had to drive down the field and score, depending on whether or not the Patriots punted. However, that doesn't take into account all of the things that can happen during a football game. For example, in some of the simulations when the Patriots went for it, the Colts got an interception return for a touchdown. This gave Indy the lead, but also gave Brady two minutes to drive down the field for a game-winning field goal. Similarly, the "safe" choice to punt sometimes resulted in a blocked punt and an instant touchdown for the Colts.

Thus, the only way to accurately find the best call is to simulate the exact game situation thousands of times, taking into account all of the different possible results that can happen in an NFL game.

The verdict: Belichick made the right call.

Breaking down the numbers, we see that when the Patriots went for it, they got the first down in 55.2% of all the simulations. After the first down, they won the game 94.3% of the time (the Colts' one timeout gives them the chance to get the ball back and still score a last-second touchdown, which they were able to do about 1 time in 20, even when the Patriots got the first down).

When the Patriots went for it and didn't convert, the Colts won the game 76.1% of the time. Most of these were because Peyton drove the ball 28 yards for the score. But sometimes the Colts won for another reason. For example, the Colts might score a quick touchdown, leaving Brady enough time to get a winning field goal, but still have enough time to score on the following kickoff return (leading to the Colts winning 42-37).

All-in-all, Belichick's call to go for it gave the Patriots a 62.8% chance of winning the game.

On the flip side, punting the ball only gave the Patriots a 41.3% chance of winning the game. That's right; the Colts won the game 58.7% of the time when the Patriots punted.

So, not only did Belichick make the right call. It wasn't even close. He made the call that increased his team's chance of winning by more than 50% (from 41.3% to 62.8%).

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