luckadjusted
NFL Week 9 · 2026

Week 15 2023 · December 16, 2023

Broncos at Lions, Week 15 2023: who deserved to win?

The Lions beat the Broncos 42–17, and the replays back it up: with the way both teams actually played, the Lions win 9 of 10.

Before kickoff the Lions were 66% favorites. The biggest swing (Q1, 11:49 left): the Broncos fumbled and the Lions recovered, worth 12 points of win probability to the Lions.

Final

Denver Broncos 17
Detroit Lions 42

December 16, 2023 · Ford Field · Closing line: Lions −5.5

Luck index +6 Lions about even · −6 Broncos

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. Broncos win 1, Lions win 9.

  1. 1 DEN 27 DET 22
  2. 2 DEN 20 DET 23
  3. 3 DEN 34 DET 40
  4. 4 DEN 21 DET 30
  5. 5 DEN 31 DET 43
  6. 6 DEN 20 DET 35
  7. 7 DEN 14 DET 33
  8. 8 DEN 20 DET 43
  9. 9 DEN 14 DET 42
  10. 10 DEN 13 DET 48

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

Broncos win 6% of them, Lions 94%. The line is what actually happened: Lions by 25.

Show as a table
Final margin in the replaysShare of replays
Broncos by 17+0.2%
Broncos by 9–161.0%
Broncos by 1–84.2%
Level after regulation0.4%
Lions by 1–811.1%
Lions by 9–1621.4%
Lions by 17+61.8%

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 +3.6 points to the Lions: the final margin was Lions by 25, without the luck Lions by 21.4. Luck shares are the fitted ones (how much of each kind is luck).

Penalties: Broncos 4 for 40 yards, Lions 2 for 54 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
Q1 7:58 Offensive Holding on the Lions, 10 yards, wiping out the play +8% DEN +2.4 pts
Q1 3:41 False Start on the Broncos, 5 yards · pre-snap +2% DET +0.6 pts
Q3 13:39 Defensive Pass Interference on the Lions (Alex Anzalone), 44 yards +3% DEN +4.4 pts
Q3 0:50 Offensive Offside on the Broncos, 4 yards, wiping out the play · pre-snap +2% DET +4.0 pts
Q4 13:03 Defensive Pass Interference on the Broncos (Fabian Moreau), 16 yards 0% DET +0.9 pts
Q4 11:05 Unnecessary Roughness on the Broncos (Tremon Smith), 15 yards 0% DET +1.4 pts

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

When it happened

Lions’ chance of winning

As low as 38% and as high as 100%. 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 Lions were ahead in it, below while the Broncos were.
#WhenWhat happenedWin probability forNext drive
1 Q1 13:09 The Lions were stopped on 3rd & 63rd & 4th downs · 41% expected +4% DEN DET: Punt
2 Q1 11:49 The Broncos fumbled and the Lions recoveredFumble bounces · loose balls are close to 50/50 +12% DET DEN: Punt
3 Q1 10:30 The Lions were stopped on 3rd & 53rd & 4th downs · 45% expected +4% DEN DET: Punt
4 Q1 8:56 The Broncos got away with an interception-worthy throwInterceptions · defenses catch 49% of interception-worthy throws +6% DEN DEN: Punt
5 Q1 7:58 Offensive Holding on the Lions, 10 yards, wiping out the playJudgment calls +8% DEN DEN: Punt
6 Q1 3:22 The Broncos converted 3rd & 93rd & 4th downs · 26% expected +8% DEN DEN: Punt
7 Q1 1:52 A. Trautman dropped a catchable passDrops · 0 drops on 43 catchable balls before this +5% DET DEN: Punt
8 Q2 13:53 The Lions converted 3rd & 53rd & 4th downs · 44% expected +7% DET DET: Touchdown

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.

  • Alim McNeill (DET DT), out (IR) · 0.3 pts
  • Riley Patterson (DET K), out · 0.3 pts
  • Scott Daly (DET LS), out (IR) · 0.1 pts
  • Kareem Jackson (DEN SS), out (IR) · 0.5 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

Broncos 0% · Lions 100%

Final margin
Lions by 25
Luck in points
3.6 for the Lions
Luck-adjusted margin
Lions by 21.4
Replay with same day's form
Broncos 6% · Lions 94% 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 15 2023 games · Broncos · Lions

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