I wanted to take a look at the most impactful plays of the season as measured by win probability. As you know, ESPN provides a play-by-play win probability measure live during games. I took this data and extracted the top 5 most impactful play in each game. I also looked at how many of the top 5 most impactful plays were attributable to the defense. Below are a few highlights.

SIU

The number 1 play was actually defense holding Shaun Lester Jr. to only 2 yards on a 1 and 10 run in with 1:45 left in the first quarter. Our win probability increased 4.5% (here and elswhere, this means increased 4.5 percentage points). This is kind of a strange and boring one so I'll do the second most impactful as well. That would be the Retzlaff pass to Roberts on 4th and 4 on our opening drive, which increased our chances by 3.1%. We were heavy favorites already in this game, so you wouldn't expect a lot of big swings unless something went horribly wrong.

Top 5 plays attributed to defense: 1/5

SMU

Most impactful play was the Miles Davis run for 37 yards on 4th and 1 late in the game. We went from a 45% chance to an 80% chance to win — a swing of 35%. This also turns out to be the most impactful play of the entire season to date. You just never know when your number is going to be called. Miles Davis came up huge in this game when it mattered. 

Top 5 plays attributed to defense: 3/5

Wyoming

Another game where swings wouldn't be expected unless we started to struggle. We were already heavy favorites to start. The most impactful play was the Marion kickoff return to open the second half. Our chances went up by 5.3% to 96.5%.

Top 5 plays attributed to defense: 3/5

KState

No surprise here: the scoop and score by Prassas raised our win probability from 28% to 53% — a 25% swing (second most impactful of the season to date). Since this game was so fun, I'll do the rest of the top 5:

2. Retzlaff to Roberts TD (11.6%)

3. Batty interception (7.9%)

4. Taggart interception (6.7%)

5. Sione Moa run on 4th and 1 in 2nd quarter (6.2%)


Top 5 plays attributed to defense: 3/5

Baylor

The most impactful play was a Sawyer Robertson incomplete pass on 4th down on their second to last possession (20.7% swing). BYU should have been able to put the game away on offense but for a controversial unsporstmanlike penalty (this penalty had a -10% impact on our chances). The Wakely interception was actually very far down on the list — only a 1.5% swing. That does not at all reflect the percentage decrease in my anxiety as a result of that play. But apparently the model gave Baylor extremely low odds of coming back. What I can't measure is what the swing would have been had they completed that pass. By that measure this was probably far more impactful.

Also notable: The Miles Davis wheel route to put us up 14-0 was the 5th most impactful and the second time he made the list in a game this season.

Top 5 plays attributed to defense: 4/5

Arizona

The most impactful play was the Jakob Robinson tip-to-himself interception. We went from a 71% chance to win (about where we started the game) to an 89% chance — a swing of 18%. Since this game is fresh on our minds, I'll give the rest of the top 5.

2. LJ Martin run for 15 yards on 4th and 3 in 2Q with 14:18 left. (11%)
3. Parker Kingston double pass (9%)
4. Parker Kingston touchdown reception in 2nd quarter (6.3%)
5. Noah Fifita incomplete pass on 3rd and 1 at the end of the first half (we subsequently stopped them on a 4th down attempt) (6.2%)

Top 5 plays attributed to defense: 2/5

Negative Plays:

I also looked at the top 5 most hurtful plays. This is already long so I won't go into them all. But the two SMU interceptions and the 4th quarter Baylor interception were all huge negative swings in our chances. The Baylor interception in particular stands out (not just because I vividly remember yelling at my TV to please not throw an interception on that play). A run for no gain would have been much less hurtful than the interception. Kind of contrary to the notion that BYU was playing it too safe in the 2nd half.

Last of all, looking at all the negative plays, almost none of them are attributable to the defense. There were a handful of Sawyer Robertson and Noah Fifita passes that had a -10% swing. But almost all of the big negative plays on the year came from the offense.