luckadjusted

Week 17 2024 · December 25, 2024

Chiefs at Steelers, Week 17 2024: who deserved to win?

The Chiefs beat the Steelers 29–10, and it was no fluke: replayed with the way both teams actually played, the Chiefs win 9 of 10.

Before kickoff the Chiefs were 59% favorites.

Final

Kansas City Chiefs 29
Pittsburgh Steelers 10

December 25, 2024 · Acrisure Stadium · Closing line: Chiefs −3

Luck index +10 Chiefs about even · −10 Steelers

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 9, Steelers win 1.

  1. 1 KC 44 PIT 15
  2. 2 KC 27 PIT 3
  3. 3 KC 37 PIT 17
  4. 4 KC 28 PIT 12
  5. 5 KC 27 PIT 14
  6. 6 KC 16 PIT 6
  7. 7 KC 32 PIT 24
  8. 8 KC 34 PIT 30
  9. 9 KC 19 PIT 17
  10. 10 KC 28 PIT 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 90% of them, Steelers 10%, counting the 1% still level after regulation as half each. The line is what actually happened: Chiefs by 19.

Show as a table
Final margin in the replaysShare of replays
Chiefs by 17+51.0%
Chiefs by 9–1621.8%
Chiefs by 1–816.8%
Level after regulation1.3%
Steelers by 1–86.5%
Steelers by 9–162.1%
Steelers by 17+0.7%

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 +7.2 points to the Steelers: the final margin was Chiefs by 19, without the luck Chiefs by 26.2. 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, 32 yds made · 96% expected
  • C. Boswell, 36 yds made · 93% expected
  • Extra point missed · 70% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Chiefs 9 for 90 yards, Steelers 4 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 toward luck, pre-snap fouls mostly don’t. How calls are valued

WhenFlagWin probability for
Q1 9:23 Unsportsmanlike Conduct on the Chiefs (Xavier Worthy), 15 yards +4% PIT +1.3 pts
Q1 2:21 Offensive Holding on the Steelers (Darnell Washington), 10 yards, wiping out the play +8% KC +2.7 pts
Q2 6:35 Offensive Holding on the Chiefs, 10 yards, wiping out the play +7% PIT +2.9 pts
Q2 2:17 Defensive Too Many Men on Field on the Chiefs, 5 yards · pre-snap +5% PIT +1.6 pts
Q3 6:00 Neutral Zone Infraction on the Chiefs (Justin Reid), 5 yards · pre-snap 0% KC 0.0 pts
Q3 5:40 Offensive Holding on the Chiefs (JuJu Smith-Schuster), 10 yards +3% PIT +0.8 pts
Q3 4:32 False Start on the Chiefs, 5 yards · pre-snap +2% PIT +0.6 pts
Q4 12:44 Unsportsmanlike Conduct on the Chiefs (Travis Kelce), 15 yards +2% PIT +1.1 pts
Q4 10:40 Offensive Offside on the Steelers (Connor Heyward), 5 yards, wiping out the play · pre-snap +2% KC +2.1 pts
Q4 10:05 Taunting on the Chiefs (Jaden Hicks), 15 yards 0% PIT +1.2 pts
Q4 10:05 False Start on the Steelers (George Pickens), 5 yards · pre-snap 0% KC +0.3 pts
Q4 7:53 Offensive Holding on the Chiefs, 10 yards, wiping out the play 0% PIT +2.2 pts
Q4 0:02 False Start on the Steelers (Scott Miller), 5 yards · pre-snap 0% KC +3.4 pts

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

When it happened

Steelers’ chance of winning

As low as 0% and as high as 58%. 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 Steelers were ahead in it, below while the Chiefs were.
#WhenWhat happenedWin probability forNext drive
1 Q1 5:59 The Chiefs converted 3rd & 113rd & 4th downs · 32% expected +7% KC KC: Touchdown
2 Q1 2:21 Offensive Holding on the Steelers (Darnell Washington), 10 yards, wiping out the playJudgment calls · 5 flags in 1300 snaps before, position avg 1 per 280 +8% KC KC: Punt
3 Q2 11:47 The Steelers converted 3rd & 83rd & 4th downs · 29% expected +5% PIT PIT: Touchdown
4 Q2 6:35 Offensive Holding on the Chiefs, 10 yards, wiping out the playJudgment calls +7% PIT PIT: Punt
5 Q2 2:17 Defensive Too Many Men on Field on the Chiefs, 5 yardsPre-snap flags +5% PIT PIT: Punt
6 Q3 11:05 The Steelers converted 3rd & 143rd & 4th downs · 20% expected +6% PIT PIT: Field goal
7 Q3 9:49 The Steelers converted 3rd & 93rd & 4th downs · 28% expected +6% PIT PIT: Field goal
8 Q3 6:41 The Steelers were stopped on 3rd & 53rd & 4th downs · 39% expected +7% KC PIT: Field goal

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.

  • Joey Porter Jr. (PIT CB), out · 1.0 pts
  • Chris Jones (KC DT), out · 0.9 pts
  • Chamarri Conner (KC FS), out · 0.5 pts
  • Spencer Shrader (KC K), out (IR) · 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 100% · Steelers 0%

Final margin
Chiefs by 19
Luck in points
7.2 for the Steelers
Luck-adjusted margin
Chiefs by 26.2
Replay with same day's form
Chiefs 90% · Steelers 10% 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 17 2024 games · Chiefs · Steelers

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