luckadjusted

Week 15 2021 · December 16, 2021

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

Chiefs at Chargers, Week 15 2021: who deserved to win?

The Chiefs beat the Chargers 34–28 and were the better team on the day: replayed with the same form, they win 7 of 10.

Before kickoff the Chiefs were 59% favorites. The biggest swing (Q4, 11:02 left): the Chargers were stopped on 3rd & 1, worth 35 points of win probability to the Chiefs.

Final (OT)

Kansas City Chiefs 34
Los Angeles Chargers 28

December 16, 2021 · SoFi Stadium · Closing line: Chiefs −3

Luck index +27 Chiefs lucky · −27 Chargers

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 7, Chargers win 3.

  1. 1 KC 58 LAC 27
  2. 2 KC 40 LAC 20
  3. 3 KC 34 LAC 19
  4. 4 KC 48 LAC 36
  5. 5 KC 40 LAC 31
  6. 6 KC 26 LAC 21
  7. 7 KC 29 LAC 26
  8. 8 KC 26 LAC 29
  9. 9 KC 20 LAC 27
  10. 10 KC 16 LAC 33

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 73% of them, Chargers 27%, counting the 5% still level after regulation as half each. The line is what actually happened: Chiefs by 6.

Show as a table
Final margin in the replaysShare of replays
Chiefs by 17+26.8%
Chiefs by 9–1619.8%
Chiefs by 1–823.9%
Level after regulation4.6%
Chargers by 1–814.6%
Chargers by 9–167.1%
Chargers by 17+3.2%

Where the luck was

Take the luck out

The final margin was Chiefs by 6. Remove the luck, one kind at a time, and it becomes Chiefs by 5.2.

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, 30 yds made · 98% expected
  • H. Butker, 33 yds made · 96% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

Chargers’ chance of winning

As low as 0% and as high as 91%. 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 Chargers were ahead in it, below while the Chiefs were.
#WhenWhat happenedWin probability forNext drive
1 Q2 0:03 The Chargers were stopped on 4th & 13rd & 4th downs · 68% expected +10% KC LAC: Turnover on downs
2 Q3 6:24 The Chiefs converted 3rd & 103rd & 4th downs · 33% expected +17% KC KC: Turnover on downs
3 Q3 1:50 The Chiefs were stopped on 4th & 13rd & 4th downs · 72% expected +19% LAC KC: Turnover
4 Q4 11:02 The Chargers were stopped on 3rd & 13rd & 4th downs · 69% expectedThe Chargers fumbled and the Chiefs recoveredFumble bounces · loose balls are close to 50/50 +35% KC LAC: Touchdown
5 Q4 9:39 The Chiefs were stopped on 3rd & 33rd & 4th downs · 58% expected +21% LAC KC: Touchdown
6 Q4 8:55 The Chiefs converted 3rd & 53rd & 4th downs · 47% expected +17% KC KC: Touchdown
7 Q4 7:44 The Chiefs’ two-point try was good3rd & 4th downs · 47% expectedRoughing the Passer on the Chargers (Joey Bosa), 15 yardsJudgment calls · 18 flags in 2067 snaps before, position avg 1 per 409 +21% KC KC: Touchdown
8 Q4 2:24 The Chargers converted 3rd & 63rd & 4th downs · 32% expected +14% LAC LAC: 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.

  • Rashawn Slater (LAC T), out (IR) · 1.0 pts
  • L'Jarius Sneed (KC CB), out · 0.7 pts
  • Chris Jones (KC DT), out (IR) · 0.7 pts
  • Mike Remmers (KC T), out (IR) · 0.6 pts
  • Andrew Wylie (KC G), 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 80% · Chargers 20%

Final margin
Chiefs by 6
Luck in points
0.8 for the Chiefs
Luck-adjusted margin
Chiefs by 5.2
Replay with same day's form
Chiefs 73% · Chargers 27% 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 15 2021 games · Chiefs · Chargers

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