luckadjusted
NFL Week 9 · 2026

Week 1 2023 · September 7, 2023

Lions at Chiefs, Week 1 2023: who deserved to win?

The Lions beat the Chiefs 21–20, but the replays lean toward the Chiefs: they take 8 of 10 with the same day's form. Luck ran their way: drops alone were worth 33 points of win probability to the Lions.

Before kickoff the Chiefs were 62% favorites. The biggest swing (Q3, 11:04 left): Return touchdown by the Lions, worth 35 points of win probability to the Lions.

Final

Detroit Lions 21
Kansas City Chiefs 20

September 7, 2023 · GEHA Field at Arrowhead Stadium · Closing line: Chiefs −4

Luck index +79 Lions very lucky · −79 Chiefs

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. Lions win 2, Chiefs win 8.

  1. 1 DET 29 KC 17
  2. 2 DET 27 KC 24
  3. 3 DET 20 KC 22
  4. 4 DET 33 KC 37
  5. 5 DET 30 KC 37
  6. 6 DET 17 KC 27
  7. 7 DET 23 KC 37
  8. 8 DET 17 KC 34
  9. 9 DET 33 KC 54
  10. 10 DET 17 KC 47

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, drop, conversion and judgment call redrawn; everything else fixed. The narrowest view of luck.

How 4,000 replays ended

Lions win 21% of them, Chiefs 79%, counting the 3% still level after regulation as half each. The line is what actually happened: Lions by 1.

Show as a table
Final margin in the replaysShare of replays
Lions by 17+2.3%
Lions by 9–165.8%
Lions by 1–811.8%
Level after regulation2.6%
Chiefs by 1–827.3%
Chiefs by 9–1620.3%
Chiefs by 17+29.9%

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 +5.4 points to the Lions: the final margin was Lions by 1, without the luck Chiefs by 4.4. 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 the weather), and what happened.

  • H. Butker, 35 yds made · 94% expected
  • H. Butker, 39 yds made · 90% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Lions 4 for 63 yards, Chiefs 3 for 25 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 half toward luck; pre-snap fouls, which repeat, don’t count. How calls are valued

WhenFlagWin probability for
Q2 1:13 Offensive Holding on the Chiefs, 10 yards, wiping out the play +4% DET +1.1 pts
Q3 3:07 Defensive Pass Interference on the Lions (Cameron Sutton), 41 yards +9% KC +2.6 pts
Q3 2:06 Tripping on the Lions (David Montgomery), 12 yards +3% KC +1.4 pts
Q4 10:46 Delay of Game on the Lions, 5 yards · pre-snap +3% KC +0.8 pts
Q4 5:07 False Start on the Lions, 5 yards · pre-snap +4% KC +0.5 pts
Q4 2:25 Offensive Holding on the Chiefs, 10 yards, wiping out the play +28% DET +2.2 pts
Q4 2:09 False Start on the Chiefs, 5 yards · pre-snap +3% DET +0.2 pts

Lions penalties, every game · Chiefs penalties, every game · All teams, 2023

When it happened

Chiefs’ chance of winning

As low as 0% and as high as 86%. Numbers mark the biggest luck moments, listed below.

nflfastR’s in-game win probability. It ignores the betting line, so it starts near even. Shaded above the middle while the Chiefs were ahead in it, below while the Lions were.
#WhenWhat happenedWin probability forNext drive
1 Q2 1:07 The Chiefs converted 3rd & 173rd & 4th downs · 23% expected +11% KC KC: Touchdown
2 Q3 11:04 The Chiefs were intercepted on a well-placed throwInterceptions · defenses pick off well under 1% of clean throwsReturn touchdown by the LionsSpecial teams +35% DET KC: Punt
3 Q3 3:07 Defensive Pass Interference on the Lions (Cameron Sutton), 41 yardsJudgment calls · 10 flags in 3498 snaps before, position avg 1 per 216 +9% KC KC: Field goal
4 Q4 5:51 The Chiefs were stopped on 3rd & 13rd & 4th downs · 78% expected +9% DET KC: Punt
5 Q4 2:33 The Lions were stopped on 4th & 23rd & 4th downs · 64% expected +23% KC DET: End of game
6 Q4 2:25 Offensive Holding on the Chiefs, 10 yards, wiping out the playJudgment calls +28% DET DET: End of game
7 Q4 2:19 S. Moore dropped a catchable passDrops · 2 drops on 31 catchable balls before this +13% DET KC: Turnover on downs
8 Q4 2:09 The Chiefs were stopped on 4th & 253rd & 4th downs · 18% expectedFalse Start on the Chiefs, 5 yardsPre-snap flags +10% DET KC: End of game

Missing players

Key players (usually on the field for half the snaps or more) who missed this game or part of it, valued by position and quality. The same players are missing in every replay, so this counts as luck in points only.

  • Travis Kelce (KC TE), out · 1.0 pts
  • Chris Jones (KC DT), out (IR) · 0.8 pts
  • Isaiah Buggs (DET DT), out · 0.2 pts

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

Lions 27% · Chiefs 73%

Final margin
Lions by 1
Luck in points
5.4 for the Lions
Luck-adjusted margin
Chiefs by 4.4
Replay with same day's form
Lions 21% · Chiefs 79% 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 win probability from nflfastR via nflverse; kicks valued against each kicker’s own record; drops and interception-worthy throws from FTN charting; injuries from snap counts and injury reports.

Methodology and validation · All Week 1 2023 games · Lions · Chiefs

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