luckadjusted
CFB Week 4 · 2026

Week 3 2025 · September 13, 2025

USC at Purdue, Week 3 2025: who deserved to win?

USC beat Purdue 33–17, and the replays lean its way: with the same day's form, it wins 7 of 10.

Before kickoff USC was a 91% favorite.

Final

USC Trojans 33
Purdue Boilermakers 17

September 13, 2025 · Ross-Ade Stadium · Closing line: USC −20.5

Luck index +26 USC lucky · −26 Purdue

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 7, Purdue wins 3.

  1. 1 USC 45 PUR 14
  2. 2 USC 26 PUR 3
  3. 3 USC 49 PUR 31
  4. 4 USC 31 PUR 17
  5. 5 USC 20 PUR 10
  6. 6 USC 27 PUR 21
  7. 7 USC 17 PUR 14
  8. 8 USC 21 PUR 24
  9. 9 USC 17 PUR 23
  10. 10 USC 21 PUR 35

Three other ways to ask

Each answers a different question, so none of them replaces the replay above.

The closing betting line, turned into a probability. What everyone knew before the 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.

Every kick, fumble bounce, conversion and judgment call redrawn; everything else fixed. The narrowest view of luck.

How 4,000 replays ended

USC wins 74% of them, Purdue 26%, counting the 5% still level after regulation as half each. The line is what actually happened: USC by 16.

Show as a table
Final margin in the replaysShare of replays
USC by 17+30.3%
USC by 9–1619.8%
USC by 1–821.1%
Level after regulation4.8%
Purdue by 1–813.9%
Purdue by 9–166.3%
Purdue by 17+3.9%

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.

Swings add up across a game, so in one that went back and forth they can pass 100%. On the scoreboard the same luck was worth +7.3 points to Purdue: the final margin was USC by 16, without the luck USC by 23.3. Luck shares are the fitted ones (how much of each kind is luck).

The kicks

How likely each kicker was to make that kick (his own record, the distance), and what happened.

  • R. Sayeri, 24 yds made · 92% expected
  • S. Porath, 39 yds made · 72% expected
  • R. Sayeri, 37 yds made · 78% expected
  • R. Sayeri, 48 yds made · 58% expected
  • R. Sayeri, 37 yds missed · 79% expected
  • R. Sayeri, 19 yds made · 95% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: USC 8 for 90 yards, Purdue 5 for 60 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

WhenFlagWin probability for
Q1 10:44 Sideline Interference on USC, 15 yards +1% PUR +1.6 pts
Q1 10:16 Pass Interference on Purdue, 15 yards 0% USC +0.8 pts
Q1 0:56 Holding on USC, 10 yards 0% PUR +0.1 pts
Q2 12:59 Personal Foul on USC, 15 yards +2% PUR +3.8 pts
Q2 11:35 Personal Foul on USC, 15 yards +1% PUR +0.7 pts
Q2 5:44 False Start on USC, 5 yards · pre-snap 0% PUR +0.6 pts
Q2 2:49 Holding on Purdue, 10 yards 0% USC +1.3 pts
Q2 2:31 Holding on USC, 10 yards 0% PUR +1.0 pts
Q3 14:18 Pass Interference on Purdue, 15 yards 0% USC +1.6 pts
Q3 2:15 Sideline Interference on USC, 15 yards +3% PUR +6.8 pts
Q4 6:07 Offside on USC, 5 yards · pre-snap +1% PUR +1.3 pts
Q4 4:03 Personal Foul on Purdue, 15 yards 0% USC +1.6 pts
Q4 0:50 False Start on Purdue, 5 yards · pre-snap 0% USC +0.1 pts

When it happened

Purdue’s chance of winning

Numbers mark the biggest luck moments, listed below.

Our in-game win probability: the score, the value of the possession and the time left, starting from the betting line. Overtime has no clock and is drawn at a fixed width. Shaded above the middle while Purdue was ahead in it, below while USC was.
#WhenWhat happenedWin probability forNext drive
1 Q1 13:41 Purdue converted 4th & 13rd & 4th downs · 69% expected +2% PUR PUR: Punt
2 Q1 10:44 Sideline Interference on USC, 15 yardsJudgment calls +1% PUR PUR: Turnover
3 Q1 8:10 USC converted 3rd & 33rd & 4th downs · 50% expected +1% PUR USC: Field goal
4 Q1 2:34 USC converted 3rd & 103rd & 4th downs · 32% expected +2% USC USC: Touchdown
5 Q2 12:59 Personal Foul on USC, 15 yardsJudgment calls +2% PUR PUR: Field goal
6 Q2 11:54 Purdue converted 3rd & 43rd & 4th downs · 39% expected +1% PUR PUR: Field goal
7 Q2 8:20 USC converted 4th & 43rd & 4th downs · 51% expected +2% USC USC: Touchdown
8 Q3 3:22 Purdue converted 3rd & 43rd & 4th downs · 39% expected +1% PUR PUR: End of half

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 100% · Purdue 0%

Final margin
USC by 16
Luck in points
7.3 for Purdue
Luck-adjusted margin
USC by 23.3
Replay with same day's form
USC 74% · Purdue 26% unchanged: why
How much of each is luck?

0% treats it as skill, 100% as pure luck. The tick is our fit.

What counts

None by default: our tests measured no carryover after a lucky break. Slide it up to count a break for more than its own swing. Why

Flip a play

Force the other outcome, in this game and in every replay: a made kick becomes a miss, a stop becomes a conversion, a flag goes the other way.

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 3 2025 games · USC · Purdue

More from Week 3 2025

Every week 3 game, 2025