luckadjusted

Week 18 2024 · January 5, 2025

Chiefs at Broncos, Week 18 2024: who deserved to win?

The Broncos beat the Chiefs 38–0, and it was no fluke: replayed with the way both teams actually played, the Broncos win 10 of 10.

Before kickoff the Broncos were 78% favorites.

Final

Kansas City Chiefs 0
Denver Broncos 38

January 5, 2025 · Empower Field at Mile High · Closing line: Broncos −10.5

Luck index +2 Broncos about even · −2 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. Chiefs win 0, Broncos win 10.

  1. 1 KC 21 DEN 24
  2. 2 KC 14 DEN 20
  3. 3 KC 14 DEN 23
  4. 4 KC 16 DEN 27
  5. 5 KC 17 DEN 30
  6. 6 KC 3 DEN 19
  7. 7 KC 10 DEN 28
  8. 8 KC 6 DEN 27
  9. 9 KC 10 DEN 34
  10. 10 KC 3 DEN 34

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

Chiefs win 2% of them, Broncos 98%. The line is what actually happened: Broncos by 38.

Show as a table
Final margin in the replaysShare of replays
Chiefs by 17+0.1%
Chiefs by 9–160.3%
Chiefs by 1–82.1%
Level after regulation0.3%
Broncos by 1–87.4%
Broncos by 9–1622.0%
Broncos by 17+67.9%

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 +14.1 points to the Broncos: the final margin was Broncos by 38, without the luck Broncos by 23.9. 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, 51 yds missed · 71% expected
  • W. Lutz, 33 yds made · 93% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Chiefs 3 for 15 yards, Broncos 5 for 41 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 11:55 Defensive Too Many Men on Field on the Chiefs, 5 yards · pre-snap 0% DEN 0.0 pts
Q1 4:53 Defensive Pass Interference on the Broncos (Patrick Surtain II), 11 yards +1% KC +0.7 pts
Q1 3:08 False Start on the Chiefs (Joshua Williams), 5 yards · pre-snap 0% KC +0.4 pts
Q2 12:08 Offensive Pass Interference on the Broncos (Lil'Jordan Humphrey), 10 yards +3% KC +1.6 pts
Q2 1:52 False Start on the Chiefs, 5 yards · pre-snap +1% DEN +0.3 pts
Q2 1:04 Illegal Forward Pass on the Broncos (Bo Nix), 5 yards 0% KC +0.5 pts
Q2 0:42 Offensive Holding on the Broncos, 10 yards, wiping out the play +3% KC +3.6 pts
Q4 1:14 Delay of Game on the Broncos, 5 yards · pre-snap 0% KC +0.1 pts

Chiefs penalties, every game · Broncos penalties, every game · All teams, 2024

When it happened

Broncos’ chance of winning

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 Broncos were ahead in it, below while the Chiefs were.
#WhenWhat happenedWin probability forNext drive
1 Q1 11:55 The Chiefs fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50Defensive Too Many Men on Field on the Chiefs, 5 yardsPre-snap flags +5% KC KC: Punt
2 Q1 10:38 The Chiefs were stopped on 3rd & 33rd & 4th downs · 51% expected +2% DEN KC: Punt
3 Q1 9:23 The Broncos converted 3rd & 43rd & 4th downs · 46% expected +3% DEN DEN: Touchdown
4 Q1 7:24 The Broncos were stopped on 3rd & 23rd & 4th downs · 61% expected +3% KC DEN: Touchdown
5 Q1 6:54 The Broncos converted 4th & 13rd & 4th downs · 73% expected +5% DEN DEN: Touchdown
6 Q2 12:08 Offensive Pass Interference on the Broncos (Lil'Jordan Humphrey), 10 yardsJudgment calls · 5 flags in 1539 snaps before, position avg 1 per 409 +3% KC KC: Missed field goal
7 Q2 3:07 The Chiefs converted 4th & 43rd & 4th downs · 45% expected +3% KC KC: Missed field goal
8 Q2 0:42 Offensive Holding on the Broncos, 10 yards, wiping out the playJudgment calls +3% KC KC: End of half

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.

  • Patrick Mahomes (KC QB), out, replaced by c.wentz · 8.1 pts
  • Trent McDuffie (KC CB), out · 1.4 pts
  • Travis Kelce (KC TE), out · 1.1 pts
  • Jawaan Taylor (KC T), out · 1.0 pts
  • Chris Jones (KC DT), out · 0.8 pts
  • Justin Reid (KC SS), out · 0.5 pts
  • Nick Bolton (KC LB), out · 0.4 pts
  • Spencer Shrader (KC K), out (IR) · 0.3 pts
  • Drue Tranquill (KC LB), out · 0.3 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

Chiefs 0% · Broncos 100%

Final margin
Broncos by 38
Luck in points
14.1 for the Broncos
Luck-adjusted margin
Broncos by 23.9
Replay with same day's form
Chiefs 2% · Broncos 98% unchanged: why
How much of each is luck?

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

What counts

We tested momentum on 19,000 lucky breaks and found none, so it's off by default. 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 18 2024 games · Chiefs · Broncos

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