Week 5 2025 · September 27, 2025
USC at Illinois, Week 5 2025: who deserved to win?
Illinois beat USC 34–32, and the replays lean its way: with the same day's form, it wins 8 of 10. USC had the bounces: kicks alone were worth 22 points of win probability to USC.
An off day for USC: its defense played far below its usual level. In a fresh game against Illinois it would win 62% of the time; with this day’s form, 24%. The numbers
Before kickoff USC was a 66% favorite. The biggest swing (Q4, 0:00 left): D. Olano made a 41-yard field goal, worth 27 points of win probability to USC.
Final
 USC Trojans | 32 |
|---|---|
 Illinois Fighting Illini | 34 |
Replay with same day's form
Luck index +24 Illinois about even · −24 USC
Each team’s own plays from this game, resampled into new drives 4,000 times: with the way both teams actually played, how often does this performance win? How the replay works
Ten replays. USC wins 2, Illinois wins 8.
- 1 USC 42 ILL 28
- 2 USC 31 ILL 27
- 3 USC 31 ILL 34
- 4 USC 21 ILL 28
- 5 USC 24 ILL 34
- 6 USC 28 ILL 41
- 7 USC 14 ILL 31
- 8 USC 21 ILL 42
- 9 USC 28 ILL 52
- 10 USC 24 ILL 56
Three other ways to ask
Each answers a different question, so none of them replaces the replay above.
Before kickoff
The closing betting line, turned into a probability. What everyone knew before the game.
Same teams, fresh game
The line plus what this game showed, weighted by how much one game can tell. It stays close to the line because one game says little.
Only coin-flips re-rolled
Every kick, fumble bounce, conversion and judgment call redrawn; everything else fixed. The narrowest view of luck.
An off day for USC
Its defense played far below its usual level. In a fresh game against Illinois it would win 62% of the time; with this day’s form, 24%.
Same teams, fresh game
Replay with same day's form
38 points apart for USC: the gap is how differently this game went from what the two teams usually are.
| Unit | This game | Usual level | Better or worse than usual |
|---|---|---|---|
| USC offenseEPA per play gained | +0.41 | +0.16 | better by 0.25 |
| USC defenseEPA per play allowed | +0.43 | +0.08 | worse by 0.35 |
| Illinois offenseEPA per play gained | +0.43 | +0.08 | better by 0.35 |
| Illinois defenseEPA per play allowed | +0.41 | +0.10 | worse by 0.30 |
EPA (expected points added) per play on competitive snaps, turnovers left out because they are valued as luck. Usual level: the team’s earlier games this season plus half of last season, pulled toward the league average. One team’s defense and the other team’s offense are the same snaps, so one game can’t fully say whose day it was; it shows how far this one was from both teams’ norms.
How 4,000 replays ended
USC wins 24% of them, Illinois 76%, counting the 4% still level after regulation as half each. The line is what actually happened: Illinois by 2.
Show as a table
| Final margin in the replays | Share of replays |
|---|---|
| USC by 17+ | 4.6% |
| USC by 9–16 | 5.8% |
| USC by 1–8 | 13.0% |
| Level after regulation | 4.5% |
| Illinois by 1–8 | 20.5% |
| Illinois by 9–16 | 19.4% |
| Illinois by 17+ | 32.2% |
Where the luck was
What the luck was worth
Every lucky and unlucky play, weighted by the moment it happened: its swing in win probability, added up by kind. A missed kick in a decided game counts for nothing; the same kick at the end of a tie game can be most of a win.
The kicks
How likely each kicker was to make that kick (his own record, the distance), and what happened.
- R. Sayeri, 21 yds made · 94% expected
- D. Olano, 45 yds made · 65% expected
- D. Olano, 41 yds made · 73% expected
Penalties: USC 7 for 49 yards, Illinois 5 for 33 yards
Every accepted flag, in order, and what it did to the helped team’s chance of winning at that moment, including any play it wiped out (points on the scoreboard in grey). A flag in a decided game is worth nothing; one at the turn of a close game can be worth most of a win. Judgment calls count toward luck, pre-snap fouls mostly don’t. How calls are valued
| When | Flag | Win probability for |
|---|---|---|
| Q1 7:36 | Personal Foul on USC, 15 yards | +2% ILL +1.1 pts |
| Q1 5:49 | Offside on USC, 2 yards · pre-snap | +2% USC +1.1 pts |
| Q1 2:04 | Pass Interference on Illinois, 9 yards | +3% USC +1.6 pts |
| Q2 10:49 | Roughing the Passer on USC, 0 yards | 0% ILL 0.0 pts |
| Q2 10:44 | Delay of Game on USC, 5 yards · pre-snap | +1% USC +0.7 pts |
| Q2 8:59 | Ineligible Downfield on USC, 5 yards, wiping out the play | +21% ILL +7.7 pts |
| Q2 1:56 | Holding on Illinois, 10 yards | +2% USC +0.9 pts |
| Q3 9:09 | False Start on Illinois, 5 yards · pre-snap | +3% USC +1.1 pts |
| Q3 5:18 | Intentional Grounding on USC, 10 yards | +6% ILL +2.8 pts |
| Q4 14:54 | Personal Foul on Illinois, 4 yards | 0% USC +0.2 pts |
| Q4 11:57 | Illegal Substitution on Illinois, 5 yards · pre-snap | +1% ILL +0.8 pts |
| Q4 0:55 | Pass Interference on USC, 12 yards | +4% ILL +0.4 pts |
When it happened
Illinois’s chance of winning
As low as 27% and as high as 100%. Numbers mark the biggest luck moments, listed below.
| # | When | What happened | Win probability for | Next drive |
|---|---|---|---|---|
| 1 | Q2 8:59 | Ineligible Downfield on USC, 5 yards, wiping out the playJudgment calls | +21% ILL | ILL: Turnover |
| 2 | Q2 8:12 | USC converted 3rd & 153rd & 4th downs · 24% expected | +7% USC | USC: Turnover on downs |
| 3 | Q2 4:37 | USC was stopped on 4th & 63rd & 4th downs · 41% expected | +6% ILL | USC: Field goal |
| 4 | Q2 0:49 | Illinois fumbled and USC recoveredFumble bounces · loose balls are close to 50/50 | +8% USC | ILL: End of half |
| 5 | Q3 4:44 | USC converted 3rd & 163rd & 4th downs · 23% expected | +7% USC | USC: Touchdown |
| 6 | Q4 9:54 | USC was stopped on 3rd & 83rd & 4th downs · 36% expectedUSC converted 4th & 83rd & 4th downs · 35% expectedUSC’s two-point try was good3rd & 4th downs · 46% expected | +11% USC | USC: Touchdown |
| 7 | Q4 6:21 | Illinois fumbled and USC recoveredFumble bounces · loose balls are close to 50/50 | +7% USC | ILL: Field goal |
| 8 | Q4 0:00 | D. Olano made a 41-yard field goalKicks · 73% expected for him | +27% USC | – |
Adjust the assumptions
Disagree with how much of a fumble bounce or a pass interference call is luck? Change it and the coin-flip replay reruns in your browser.
Only coin-flips re-rolled
USC 13% · Illinois 87%
- Final margin
- Illinois by 2
- Luck in points
- 5.7 for USC
- Luck-adjusted margin
- Illinois by 7.7
- Replay with same day's form
- USC 24% · Illinois 76% unchanged: why
About these numbers
Play-by-play and expected points from CollegeFootballData.com via cfbfastR; win probability from our own model of the score, the possession and the betting line; kicks valued against each kicker’s own record. College play-by-play has no charting of drops or interception-worthy throws and no injury reports, so those kinds of luck aren’t counted here.
Methodology and validation · All Week 5 2025 games · 
USC · 
Illinois
More from Week 5 2025
- Oregon at Penn State ORE 30–24 · replay 39% for the winner
- Rutgers at Minnesota MINN 31–28 · replay 41% for the winner
- Indiana at Iowa IU 20–15 · replay 48% for the winner
- UCLA at Northwestern NU 17–14 · replay 66% for the winner
- Ohio State at Washington OSU 24–6 · replay 79% for the winner
- Hawai'i at Air Force HAW 44–35 · replay 5% for the winner
- Louisville at Pittsburgh LOU 34–27 · replay 11% for the winner
- California at Boston College CAL 28–24 · replay 28% for the winner
- Marshall at Louisiana UL 54–51 · replay 29% for the winner
- Cincinnati at Kansas CIN 37–34 · replay 30% for the winner
- Houston at Oregon State HOU 27–24 · replay 34% for the winner
- Georgia Tech at Wake Forest GT 30–29 · replay 40% for the winner