luckadjusted

Wild Card 2021 · January 16, 2022

No FTN charting for this game (drops and interception-worthy throws are not modelled).

Steelers at Chiefs, Wild Card 2021: who deserved to win?

The Chiefs beat the Steelers 42–21, and it was no fluke: replayed with the way both teams actually played, the Chiefs win 10 of 10.

Before kickoff the Chiefs were 83% favorites. The biggest swing (Q2, 10:51 left): Return touchdown by the Steelers, worth 18 points of win probability to the Steelers.

Final

Pittsburgh Steelers 21
Kansas City Chiefs 42

January 16, 2022 · GEHA Field at Arrowhead Stadium · Closing line: Chiefs −13

Luck index +1 Chiefs about even · −1 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. Steelers win 0, Chiefs win 10.

  1. 1 PIT 16 KC 20
  2. 2 PIT 33 KC 42
  3. 3 PIT 33 KC 46
  4. 4 PIT 24 KC 41
  5. 5 PIT 27 KC 47
  6. 6 PIT 14 KC 37
  7. 7 PIT 17 KC 44
  8. 8 PIT 14 KC 45
  9. 9 PIT 23 KC 58
  10. 10 PIT 3 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

Steelers win 1% of them, Chiefs 99%. The line is what actually happened: Chiefs by 21.

Show as a table
Final margin in the replaysShare of replays
Steelers by 17+0.0%
Steelers by 9–160.2%
Steelers by 1–81.0%
Level after regulation0.3%
Chiefs by 1–83.8%
Chiefs by 9–1610.5%
Chiefs by 17+84.2%

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 +1.1 points to the Chiefs: the final margin was Chiefs by 21, without the luck Chiefs by 19.9. Luck shares are the fitted ones (how much of each kind is luck).

Penalties: Steelers 4 for 45 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 toward luck, pre-snap fouls mostly don’t. How calls are valued

WhenFlagWin probability for
Q1 4:15 False Start on the Steelers (Diontae Johnson), 5 yards · pre-snap +2% KC +0.4 pts
Q1 1:38 False Start on the Chiefs, 5 yards · pre-snap +2% PIT +0.6 pts
Q2 11:13 Face Mask on the Steelers (T.J. Watt), 15 yards +3% KC +1.2 pts
Q2 8:42 False Start on the Chiefs (Blake Bell), 5 yards · pre-snap +1% PIT +0.9 pts
Q2 2:00 Roughing the Passer on the Steelers (Alex Highsmith), 15 yards +3% KC +1.2 pts
Q4 11:37 Offensive Holding on the Steelers, 10 yards 0% KC +0.8 pts
Q4 11:28 Roughing the Passer on the Chiefs (Alex Okafor), 15 yards, wiping out the play 0% PIT +5.4 pts

Steelers penalties, every game · Chiefs penalties, every game · All teams, 2021

When it happened

Chiefs’ chance of winning

As low as 37% 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 Chiefs were ahead in it, below while the Steelers were.
#WhenWhat happenedWin probability forNext drive
1 Q1 13:36 The Steelers were stopped on 3rd & 103rd & 4th downs · 26% expected +4% KC PIT: Punt
2 Q1 11:10 The Steelers were stopped on 3rd & 83rd & 4th downs · 30% expected +4% KC PIT: Punt
3 Q1 7:19 The Steelers were stopped on 3rd & 23rd & 4th downs · 59% expected +7% KC PIT: Punt
4 Q1 4:15 The Steelers were stopped on 3rd & 133rd & 4th downs · 22% expectedFalse Start on the Steelers (Diontae Johnson), 5 yardsPre-snap flags · 15 flags in 2520 snaps before, position avg 1 per 399 +4% KC PIT: Punt
5 Q1 1:38 The Chiefs converted 3rd & 113rd & 4th downs · 30% expectedFalse Start on the Chiefs, 5 yardsPre-snap flags +4% KC KC: Punt
6 Q2 10:51 The Chiefs fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50Return touchdown by the SteelersSpecial teams +18% PIT KC: Touchdown
7 Q2 2:00 The Chiefs converted 3rd & 73rd & 4th downs · 38% expectedRoughing the Passer on the Steelers (Alex Highsmith), 15 yardsJudgment calls · 6 flags in 1643 snaps before, position avg 1 per 409 +11% KC KC: Touchdown
8 Q2 0:22 The Chiefs converted 3rd & 203rd & 4th downs · 21% expected +10% KC KC: 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.

  • Rashad Fenton (KC CB), 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

Steelers 0% · Chiefs 100%

Final margin
Chiefs by 21
Luck in points
1.1 for the Chiefs
Luck-adjusted margin
Chiefs by 19.9
Replay with same day's form
Steelers 1% · Chiefs 99% 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 (not available for this game); injuries from snap counts and injury reports. No FTN charting for this game (drops and interception-worthy throws are not modelled).

Methodology and validation · All Wild Card 2021 games · Steelers · Chiefs

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