In this tumultuous Week 15, we saw the winless Colts beat the Titans, the seemingly unstoppable Packers lose to a floundering Chiefs team, and his holiness, Tim Tebow, lose for the first time in 7 games. Kansas City jumped out to a 6-0 lead with two early field goals, but just as importantly, kept the ball out of Aaron Rodgers' hands by sustaining long drives. The Chiefs' first three drives totaled 38 plays consuming over 19 minutes of game clock. Newly anointed interim head coach Romeo Crennel was also faced with a few early 4th-down decisions. Using our Markov model, we can see how these drives developed.
The Chiefs received the opening kickoff and proceeded to drive 79 yards on 14 plays, not letting the Packers offense take the field until six minutes had already run off the clock. Here is a look at how the probabilities developed throughout the drive:
Kyle Orton and company converted on two third downs (plays 3 and 9) thanks to short completions and runs after the catch, but after two incomplete pass attempts on 2nd-and-goal and 3rd-and-goal from the 1-yardline, the Chiefs decided to take the field goal.
As Advanced NFL Stats followers like yourselves will know, it almost always makes more sense to go for it on the goal line. Going for it nets almost twice as many expected points as a field goal (4.52 to 2.40) given that the estimated conversion rate is about 68%. Even if the Chiefs don't convert, they still net +0.53 expected points by pinning the Packers so deep. Now this should be qualified: this takes a league-average offense as the baseline and the Packers certainly are not a league-average offense (although they looked it on Sunday).
After a Packers missed field goal and another KC 9-play, 4+ minute drive that ended in a field goal, the Chiefs offense took the field again, this time at their own 15. What followed was an eerily similar 15-play, 9-minute drive:
This time, after Jackie Battle and Thomas Jones were stuffed on back-to-back plays, the Chiefs decided to go for it on 4th-and-1 from the 3-yardline. Similarly, going for it was the correct decision. Going for it yields 4.10 expected points while taking the field goal results in 2.38. Since it was slightly later in the game, we can take Win Probability into account as well. Going for it gives the Chiefs an 81% chance of winning the ball game versus a 79% chance if they take the field goal. Again, this should be qualified for the same reason - the Packers are not a league-average team, so those probabilities are probably lower. Given that the Chiefs were significant underdogs, however, it makes even more sense to be taking risks.
Jackie Battle was once again stuffed, but backed up against their own end zone, the Packers were forced into a quick three-and-out. This would have been a huge win for the Chiefs had Tim Masthay not unleashed a 71-yard punt to even the field position battle. No one else would score before halftime and the Chiefs would go on to strip the Packers of their undefeated season.
Given that they were severe underdogs, I don't fully understand Romeo Crennel's decision to take the field goal on the first drive. In fact, I would argue that it would have made sense for the Chiefs to go for it on 4th-and-6 from the 14 on their second drive, instead of taking the second field goal. The Field Goal attempt nets on average 0.05 expected points over going for it in that situation - essentially negligible - but the reward for a conversion is much higher. After all, underdogs need aggressive and risky strategies to win. Props to Crennel for taking the chance on the third drive, though.
Keith Goldner is the creator of Drive-By Football, and Chief Analyst at numberFire.com - The leading fantasy sports analytics platform. Follow him on twitter @drivebyfootball or check out numberFire on Facebook.