NFL Advanced Analysis: Patriots Primarily Punt on 4th Down

Where did the Aggressive Bill go? Apparently lost somewhere in the swirling winds of Foxboro.

Bill Belichick is known for being one of the greatest football minds in NFL history. He's also known for being one of the "riskiest" play-callers -- riskiest in quotes to emphasize that he actually plays to the odds rather than most of the conservative football minds. Down 28-13 in the AFC Championship game, avid Patriots fan Bill Simmons put it best: "Ravens playing to win, Pats playing not to lose."

Belichick faced eight fourth downs in the game against the Ravens, seven of which were legitimate questions for the best course of action: Go for it, punt or kick the field goal. Whereas we would normally expect Belichick to be aggressive, he seemed more reserved in his decision-making. There are a ton of factors that could explain his passive play-calling. For example, it was extremely windy making field goals more difficult and maybe Belichick did not have faith that Joe Flacco could sustain a 90-yard drive due to the Ravens boom-or-bust offense (the Ravens ended up with three scoring drives of 10+ plays including a 90-yarder and 87-yarder).

Let's look at each fourth down decision, starting with the very first. Remember in the beginning of the game, especially if the score is fairly close, we should look at expected points, but as score and time become bigger factors, we will switch to win probability. Also, note that these are league baselines. The fact that the Patriots offense is No. 1 in the league and far above league average would indicate a higher success rate on 4th-down conversion attempts.

1. Tie game, about 2 minutes into the game, 4th-and-2 from NE 42:
NE: Showed fake punt, forced BAL timeout, then punt

Go-For-It Success Rate: 60%
Expected Points[Go-For-It] = 0.00
Expected Points[Punt] = -0.42
Break Even: 50% conversion

Result: Go For It, 0.42 points forfeited (2% win probability forfeited)

2. Tie game, about 6 minutes remaining in 1st quarter, 4th-and-2 from BAL 12:
NE: Field Goal (Good)

Go-For-It Success Rate: 59%
Field Goal Success Rate: 91%
EP[Go-For-It] = +2.84
EP[Field Goal] = +2.17
Break Even: 44% conversion

Result: Go For It, 0.67 points forfeited (2% win probability forfeited)

3. Up 3, about 3 minutes remaining in 1st quarter, 4th-and-9 from BAL 35 (No man's land):
NE: Punt

Go-For-It Success Rate: 36%
Field Goal Success Rate: 50%
EP[Go-For-It] = +0.57
EP[Field Goal] = +0.42
EP[Punt] = +0.11
Break Even: 33% conversion

Result: Go For It, 0.46 points forfeited*
*This is a toss up decision and slight changes in the conversion rates change the decision dramatically. Also, up 3, all three decisions result in 61-62% win probability. As a result, we cannot reasonably say this was a poor decision.

4. Up 3, about 0:20 seconds remaining in 1st quarter, 4th-and-2 from BAL 45:
NE: Punt

Go-For-It Success Rate: 60%
EP[Go-For-It] = +0.79
EP[Punt] = -0.11
Break Even: 39% conversion

Result: Go For It, 0.90 points forfeited (1% win probability forfeited)

5. Up 3, about 1 minute remaining in 2nd quarter, 4th-and-1 from BAL 34 (No man's land):
NE: Converted on direct-snap to Danny Woodhead

Go-For-It Success Rate: 74%
Field Goal Success Rate: 52%
EP[Go-For-It] = +2.01
EP[Field Goal] = +0.54
EP[Punt] = +0.16
Break Even: 39% conversion

Result: Go For It, optimal decision

6. Up 6, about 10 minutes left in 3rd quarter, 4th-and-8 from BAL 34 (No man's land): 
NE: Punt

Go-For-It Success Rate: 38%
Field Goal Success Rate: 52%
EP[Go-For-It] = +0.70
EP[Field Goal] = +0.54
EP[Punt] = +0.16
Break Even: 35% conversion

Result: Go For It, 0.54 points forfeited*
Again, like the other 4th-and-long in no man's land, small changes in the odds make a huge difference in the decision. All win probabilities are between 74-76%, although according to win probability, punting is the optimal decision at 76%.

(7. Down 1, about 5 minutes left in 3rd quarter, 4th-and-12 from NE 23: Obvious punting situation)

8. Down 15, 8:35 left in 4th quarter, 4th-and-4 from BAL 19:
NE: Incomplete on conversion attempt

Go-For-It Success Rate: 48%
Field Goal Success Rate: 82%
Win Probability[Go-For-It] = 4%
Win Probability[Field Goal] = 4%
Break Even: 41% conversion

Result: Go For It, optimal decision

So, out of the seven questionable decisions, three of them were definitely toss-ups and a decision-maker could not really be faulted or celebrated (attempts 3, 6 and 8). Out of the remaining four, Belichick played by the numbers only once and forfeited 1.99 points (2.99 points if you include the two 4th-and-long from no man's land) and about 5% chance of winning. That does not seem significant given the final two-score outcome of the game, but those marginal subtractions add up. Optimal decision-making is not about making one call that dramatically exposes a market inefficiency, it's about the hundreds of incremental less than 1% edges that add up over the course of a season.

Again, this should be qualified in that there are always external factors that could have been affecting the Patriots conversion odds and thus, their decision-making. As a favorite (and the Patriots were heavy favorites), you do want to play low-risk strategies -- albeit without forfeiting win probability -- and punting/playing the field position game is certainly low-risk. The biggest gaffe was punting on 4th-and-2 on the Baltimore 45, which cost the Patriots almost a full point. Outside of that, the suboptimal decision-making pales in comparison to the huge second-half turnovers and inability to stop the Ravens offense. Give credit to the normally conservative Jim Caldwell for staying aggressive deep into the fourth quarter rather than the typical three run plays and out we see when teams are in the lead. In fact, Caldwell called three straight pass plays (two incompletes and a sack), barely running any time off the clock midway through the fourth quarter while up two scores. Had the Patriots come back, he would surely have been criticized for not bleeding the clock, but Caldwell knew that the best way to win was to convert and extend the drive -- and score again, if possible.

Congrats to the Ravens on another big upset, setting up the Harbaugh Bowl. Go crazy.