luckadjusted

Week 18 2021 · January 8, 2022

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

Chiefs at Broncos, Week 18 2021: who deserved to win?

The Chiefs beat the Broncos 28–24 and were the better team on the day: replayed with the same form, they win 8 of 10. The Broncos had the bounces: judgment calls alone were worth 4.2 points to the Broncos.

Before kickoff the Chiefs were 80% favorites. The biggest swing (Q4, 7:57 left): Return touchdown by the Chiefs, worth 92 points of win probability to the Chiefs.

Final

Kansas City Chiefs 28
Denver Broncos 24

January 8, 2022 · Empower Field at Mile High · Closing line: Chiefs −11.5

Luck index +21 Chiefs about even · −21 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. Chiefs win 8, Broncos win 2.

  1. 1 KC 28 DEN 3
  2. 2 KC 29 DEN 9
  3. 3 KC 27 DEN 12
  4. 4 KC 20 DEN 7
  5. 5 KC 24 DEN 14
  6. 6 KC 14 DEN 7
  7. 7 KC 24 DEN 20
  8. 8 KC 19 DEN 17
  9. 9 KC 24 DEN 27
  10. 10 KC 3 DEN 14

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 79% of them, Broncos 21%, counting the 5% still level after regulation as half each. The line is what actually happened: Chiefs by 4.

Show as a table
Final margin in the replaysShare of replays
Chiefs by 17+24.4%
Chiefs by 9–1623.8%
Chiefs by 1–826.5%
Level after regulation4.9%
Broncos by 1–813.9%
Broncos by 9–164.9%
Broncos by 17+1.6%

Where the luck was

Take the luck out

The final margin was Chiefs by 4. Remove the luck, one kind at a time, and it becomes Broncos by 2.0.

Each row takes one kind of luck out of the margin. Color shows which team it helped. Luck shares are the fitted ones (how much of each component 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, 34 yds made · 95% expected
  • H. Butker, 51 yds made · 75% expected
  • B. McManus, 31 yds made · 97% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

Broncos’ chance of winning

As low as 0% and as high as 84%. 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 5:22 Roughing the Kicker on the Chiefs, 15 yardsJudgment calls +7% DEN DEN: Touchdown
2 Q2 7:57 The Broncos converted 3rd & 73rd & 4th downs · 32% expected +8% DEN DEN: Touchdown
3 Q3 10:52 The Chiefs converted 3rd & 73rd & 4th downs · 39% expected +10% KC KC: Touchdown
4 Q3 10:01 The Broncos converted 3rd & 133rd & 4th downs · 22% expected +13% DEN DEN: Touchdown
5 Q3 2:14 The Chiefs converted 4th & 13rd & 4th downs · 78% expected +8% KC KC: Field goal
6 Q4 14:54 The Chiefs were stopped on 3rd & 63rd & 4th downs · 42% expected +7% DEN KC: Field goal
7 Q4 7:57 The Broncos fumbled and the Chiefs recoveredFumble bounces · loose balls are close to 50/50Return touchdown by the ChiefsSpecial teams +92% KC DEN: Field goal
8 Q4 6:06 The Broncos converted 3rd & 63rd & 4th downs · 35% expected +16% DEN DEN: 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.

  • Teddy Bridgewater (DEN QB), out (IR), replaced by d.lock · 4.6 pts
  • Bobby Massie (DEN T), out · 0.8 pts
  • Ronald Darby (DEN CB), out (IR) · 0.7 pts
  • Calvin Anderson (DEN T), out (IR) · 0.6 pts
  • Kareem Jackson (DEN SS), out (IR) · 0.5 pts
  • Dalton Risner (DEN G), out (IR) · 0.3 pts
  • Kenny Young (DEN LB), out · 0.2 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 83% · Broncos 17%

Final margin
Chiefs by 4
Luck in points
6.0 for the Chiefs
Luck-adjusted margin
Broncos by 2.0
Replay with same day's form
Chiefs 79% · Broncos 21% 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 18 2021 games · Chiefs · Broncos

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