Neil once pointed out, that you can approximate a team’s odds of winning a game by using the point spread and the following formula:
p(W) = 1 – (1-NORMDIST(0.5,SPREAD,13.86,TRUE))+0.5*(NORMDIST(0.5,SPREAD,13.86,TRUE)-NORMDIST(-0.5,SPREAD,13.86,TRUE))
For college football games, there is research by Wayne Winston and Jeff Sagarin that the standard deviation in the above formula should be 16 instead of 13.86. One of the nice things about the SRS is that it comes very close to approximating the point spread in each game. If we give 3 points to the home team, we can then approximate each team’s likelihood of winning in their remaining games.
For example, here is a look at Oregon’s remaining schedule and their likelihood of winning each game. Note that for now, I am assuming that the Ducks host the Trojans in the Pac-12 Championship Game:
| Tm | Opp | Loc | SRS Tm | SRS Opp | Proj Spread | Win Prob |
|---|---|---|---|---|---|---|
| Oregon | Southern Cal | Road | 65.9 | 53.9 | -8.9 | 71.2% |
| Oregon | California | Road | 65.9 | 42.3 | -20.6 | 90.1% |
| Oregon | Stanford | Home | 65.9 | 53.8 | -15 | 82.6% |
| Oregon | Oregon St | Road | 65.9 | 55.2 | -7.7 | 68.4% |
| Oregon | Southern Cal | Home | 65.9 | 53.9 | -14.9 | 82.5% |
| Total | 29.9% |
Winning five games in a row isn’t easy, even for a team as good as Oregon. With four difficult games left, the odds of them going 5-0 are just 29.9%. Things are much more favorable for Kansas State:
| Tm | Opp | Loc | SRS Tm | SRS Opp | Proj Spread | Win Prob |
|---|---|---|---|---|---|---|
| Kansas St | Oklahoma St | Home | 66.3 | 52.5 | -16.9 | 85.4% |
| Kansas St | TCU | Road | 66.3 | 46.2 | -17.1 | 85.7% |
| Kansas St | Baylor | Road | 66.3 | 46 | -17.4 | 86.1% |
| Kansas St | Texas | Home | 66.3 | 52.1 | -17.2 | 85.9% |
| Total | 54.1% |
The Big 12 has some good teams, but Kansas State appears to be an elite one. My gut tells me the SRS is underrating the likelihood of one of those teams pulling off an upset, but there’s no doubt that Kansas State would be a double-digit favorite against each of those teams right now. Of course, one thing the SRS ignores in all of these instances is the possibility of a key injury affecting any team.
Notre Dame has a history of dropping games to bad teams, but I don’t think there’s much of a chance the Fighting Irish lose any of their next three games. That means the USC game should have national title implications:
| Tm | Opp | Loc | SRS Tm | SRS Opp | Proj Spread | Win Prob |
|---|---|---|---|---|---|---|
| Notre Dame | Pittsburgh | Home | 63.1 | 37.2 | -28.9 | 96.5% |
| Notre Dame | Boston College | Road | 63.1 | 31.1 | -29.1 | 96.5% |
| Notre Dame | Wake Forest | Home | 63.1 | 27.9 | -38.3 | 99.2% |
| Notre Dame | Southern Cal | Road | 63.1 | 53.9 | -6.2 | 65.1% |
| Total | 60.1% |
There is only a 10% chance (29.9% * 54.1% * 60.1%) that Oregon, Kansas State and Notre Dame all finish the season undefeated, at least according to the assumptions in this post. If you want to look at how all three teams got here, you can check all the NCAA game scores here.