Through 13 weeks of football, both the Indianapolis Colts and New Orleans Saints are 12-0 with no huge upset special looming in the final four weeks of the season. Although both of their toughest games (Colts vs Broncos and Saints vs Cowboys) are at home, the chances of an undefeated season aren’t 100 percent or even 90 percent.
If the Colts have a 90 percent chance to win each of their remaining games, their probability of a 16-0 season is .90 x .90 x .90 x .90, or 65.6 percent. Using the Week 13 NFL ratings, we can estimate the win probability for each of their remaining games and, thus, their likelihood of an undefeated season.
For instance, the Colts (33.2 rating) play the Broncos (24.4) at home this week. That gives the Colts a 66.4 percent chance to win, using a Pythagorean formula that accounts for home field advantage. Here’s a list of the Colts’ remaining games and their predicted win probability:
Broncos 0.66 @ Jags 0.84 Jets 0.71 @ Bills 0.87
Multiplying each of these probabilities together yields a 34.7 percent chance of an undefeated season. Indianapolis’s remaining opponents have an average rating of 21.2—just under league average.
Here’s the same for the Saints:
@ Falcons 0.90 Cowboys 0.76 Buccaneers 0.94 @ Panthers 0.86
The Saints’ easier schedule (an average opponent rating of 17.8, which ranks just below the Raiders’ 17.94 rating at No. 27) gives them a 55.2 percent shot at 16-0.
