luckadjusted

Week 16 2021 · December 26, 2021

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

Steelers at Chiefs, Week 16 2021: who deserved to win?

The Chiefs beat the Steelers 36–10, and it was no fluke: replayed with the way both teams actually played, the Chiefs win 9 of 10.

Before kickoff the Chiefs were 78% favorites. The biggest swing (Q1, 6:12 left): Defensive Offside on the Steelers (Cameron Heyward), 5 yards, wiping out the play, worth 12 points of win probability to the Chiefs.

Final

Pittsburgh Steelers 10
Kansas City Chiefs 36

December 26, 2021 · GEHA Field at Arrowhead Stadium · Closing line: Chiefs −10.5

Luck index +12 Chiefs about even · −12 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 1, Chiefs win 9.

  1. 1 PIT 20 KC 14
  2. 2 PIT 10 KC 13
  3. 3 PIT 10 KC 14
  4. 4 PIT 13 KC 20
  5. 5 PIT 13 KC 23
  6. 6 PIT 0 KC 14
  7. 7 PIT 10 KC 27
  8. 8 PIT 13 KC 34
  9. 9 PIT 17 KC 41
  10. 10 PIT 7 KC 41

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 12% of them, Chiefs 88%, counting the 2% still level after regulation as half each. The line is what actually happened: Chiefs by 26.

Show as a table
Final margin in the replaysShare of replays
Steelers by 17+0.8%
Steelers by 9–162.6%
Steelers by 1–86.8%
Level after regulation1.8%
Chiefs by 1–818.8%
Chiefs by 9–1621.7%
Chiefs by 17+47.5%

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 +7.1 points to the Chiefs: the final margin was Chiefs by 26, without the luck Chiefs by 18.9. 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.

  • E. Fry, 44 yds made · 75% expected
  • C. Boswell, 36 yds missed · 90% expected
  • E. Fry, 39 yds missed · 84% expected
  • C. Boswell, 34 yds made · 92% expected
  • E. Fry, 34 yds made · 90% expected
  • E. Fry, 30 yds made · 94% expected
  • Extra point missed · 93% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Steelers 5 for 40 yards, Chiefs 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 6:12 Defensive Offside on the Steelers (Cameron Heyward), 5 yards, wiping out the play · pre-snap +12% KC +4.8 pts
Q1 3:59 Encroachment on the Steelers (Montravius Adams), 5 yards · pre-snap +1% KC +0.5 pts
Q2 0:37 False Start on the Chiefs (Byron Pringle), 5 yards · pre-snap 0% PIT +0.4 pts
Q3 13:48 Illegal Formation on the Chiefs, 5 yards · pre-snap 0% PIT +1.6 pts
Q3 8:53 Defensive Offside on the Chiefs (Deandre Baker), 5 yards · pre-snap 0% PIT +0.4 pts
Q3 6:21 Offensive Holding on the Steelers, 10 yards 0% KC +0.9 pts
Q3 5:06 Defensive Offside on the Chiefs (Chris Jones), 5 yards · pre-snap 0% PIT +0.6 pts
Q3 5:02 Taunting on the Steelers (Ray-Ray McCloud), 15 yards 0% KC +1.6 pts
Q3 3:55 Defensive Pass Interference on the Chiefs (L'Jarius Sneed), 21 yards 0% PIT +3.2 pts
Q3 3:37 False Start on the Steelers, 5 yards · pre-snap 0% KC +0.1 pts

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

When it happened

Chiefs’ 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 Chiefs were ahead in it, below while the Steelers were.
#WhenWhat happenedWin probability forNext drive
1 Q1 13:02 The Steelers were stopped on 3rd & 103rd & 4th downs · 25% expected +4% KC PIT: Punt
2 Q1 11:00 The Chiefs converted 3rd & 73rd & 4th downs · 40% expected +5% KC KC: Touchdown
3 Q1 6:12 Defensive Offside on the Steelers (Cameron Heyward), 5 yards, wiping out the playPre-snap flags · 8 flags in 2854 snaps before, position avg 1 per 273 +12% KC KC: Touchdown
4 Q1 5:26 The Chiefs converted 4th & 13rd & 4th downs · 72% expected +5% KC KC: Touchdown
5 Q1 3:13 The Chiefs converted 3rd & 23rd & 4th downs · 66% expected +3% KC KC: Touchdown
6 Q1 2:30 The Chiefs fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 +4% KC KC: Touchdown
7 Q2 6:55 The Steelers converted 3rd & 83rd & 4th downs · 28% expected +4% PIT PIT: Missed field goal
8 Q2 5:08 C. Boswell missed 36-yard field goalKicks · 90% expected for him +4% KC PIT: Turnover on downs

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 · 0.9 pts
  • Harrison Butker (KC K), out (IR) · 0.5 pts
  • Rashad Fenton (KC CB), out (IR) · 0.3 pts
  • Tommy Townsend (KC P), out (IR) · 0.2 pts
  • Pat Freiermuth (PIT TE), out · 0.9 pts
  • Kevin Dotson (PIT G), out (IR) · 0.4 pts
  • Chris Wormley (PIT DE), 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 26
Luck in points
7.1 for the Chiefs
Luck-adjusted margin
Chiefs by 18.9
Replay with same day's form
Steelers 12% · Chiefs 88% 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 Week 16 2021 games · Steelers · Chiefs

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