luckadjusted
CFB Week 4 · 2026

Week 4 2026 · September 26, 2026

Notre Dame at Purdue, Week 4 2026: who deserved to win?

Notre Dame beat Purdue 49–10, and the replays back it up: with the way both teams actually played, Notre Dame wins 10 of 10.

Before kickoff Notre Dame was a 96% favorite.

Final

Notre Dame Fighting Irish 49
Purdue Boilermakers 10

September 26, 2026 · Ross-Ade Stadium · Closing line: Notre Dame −27.5

Luck index 0 Notre Dame about even · 0 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. Notre Dame wins 10, Purdue wins 0.

  1. 1 ND 59 PUR 3
  2. 2 ND 50 PUR 0
  3. 3 ND 56 PUR 10
  4. 4 ND 45 PUR 3
  5. 5 ND 41 PUR 3
  6. 6 ND 45 PUR 10
  7. 7 ND 31 PUR 0
  8. 8 ND 31 PUR 3
  9. 9 ND 34 PUR 10
  10. 10 ND 34 PUR 17

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

Notre Dame wins 100% of them, Purdue 0%. The line is what actually happened: Notre Dame by 39.

Show as a table
Final margin in the replaysShare of replays
Notre Dame by 17+97.9%
Notre Dame by 9–161.7%
Notre Dame by 1–80.4%
Level after regulation0.1%
Purdue by 1–80.1%
Purdue by 9–160.0%
Purdue by 17+0.0%

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.

No play in this game swung win probability by luck.

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 +1.4 points to Notre Dame: the final margin was Notre Dame by 39, without the luck Notre Dame by 37.6. Luck shares are the fitted ones (how much of each kind is luck).

Penalties: Notre Dame 1 for 15 yards, Purdue 6 for 46 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 7:36 False Start on Purdue, 5 yards · pre-snap 0% ND +0.8 pts
Q2 7:58 Offside on Purdue, 5 yards · pre-snap 0% ND +0.4 pts
Q2 6:26 Pass Interference on Purdue, 13 yards 0% ND +2.6 pts
Q2 4:09 Illegal Block on Purdue, 8 yards 0% ND +0.5 pts
Q3 5:41 Illegal Shift on Purdue, 5 yards · pre-snap 0% ND +0.7 pts
Q4 13:29 Holding on Purdue, 10 yards 0% ND +0.9 pts
Q4 1:00 Pass Interference on Notre Dame, 15 yards 0% PUR +1.3 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 Notre Dame was.
#WhenWhat happenedWin probability forNext drive
1 Q1 11:39 Notre Dame was stopped on 3rd & 63rd & 4th downs · 46% expected +1% PUR ND: Punt
2 Q1 10:31 Purdue converted 3rd & 53rd & 4th downs · 43% expected +1% PUR PUR: Turnover on downs
3 Q1 8:11 Purdue converted 3rd & 13rd & 4th downs · 78% expected +0% PUR PUR: Turnover on downs
4 Q1 7:36 False Start on Purdue, 5 yardsPre-snap flags +0% ND ND: Touchdown
5 Q1 5:51 Purdue was stopped on 3rd & 43rd & 4th downs · 48% expected +1% ND PUR: Turnover on downs
6 Q1 5:46 Purdue was stopped on 4th & 43rd & 4th downs · 47% expected +1% ND PUR: Punt
7 Q1 1:49 Purdue was stopped on 3rd & 13rd & 4th downs · 77% expected +1% ND PUR: Punt
8 Q2 14:02 Purdue converted 3rd & 93rd & 4th downs · 30% expected +0% PUR PUR: Punt

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

Notre Dame 100% · Purdue 0%

Final margin
Notre Dame by 39
Luck in points
1.4 for Notre Dame
Luck-adjusted margin
Notre Dame by 37.6
Replay with same day's form
Notre Dame 100% · Purdue 0% 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 4 2026 games · Notre Dame · Purdue

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