luckadjusted
NFL Week 9 · 2026

Week 3 2021 · September 26, 2021

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

Chargers at Chiefs, Week 3 2021: who deserved to win?

The Chargers beat the Chiefs 30–24, but the replays lean toward the Chiefs: they take 7 of 10 with the same day's form. Luck ran their way: fumble bounces alone were worth 26 points of win probability to the Chargers.

Before kickoff the Chiefs were 68% favorites. The biggest swing (Q4, 2:35 left): Illegal Shift on the Chargers (Jared Cook), 5 yards, wiping out the play, worth 17 points of win probability to the Chiefs.

Final

Los Angeles Chargers 30
Kansas City Chiefs 24

September 26, 2021 · GEHA Field at Arrowhead Stadium · Closing line: Chiefs −6.5

Luck index +67 Chargers very lucky · −67 Chiefs

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. Chargers win 3, Chiefs win 7.

  1. 1 LAC 34 KC 17
  2. 2 LAC 20 KC 13
  3. 3 LAC 17 KC 14
  4. 4 LAC 17 KC 20
  5. 5 LAC 9 KC 13
  6. 6 LAC 23 KC 30
  7. 7 LAC 20 KC 31
  8. 8 LAC 19 KC 34
  9. 9 LAC 17 KC 35
  10. 10 LAC 10 KC 38

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

Chargers win 33% of them, Chiefs 67%, counting the 2% still level after regulation as half each. The line is what actually happened: Chargers by 6.

Show as a table
Final margin in the replaysShare of replays
Chargers by 17+4.7%
Chargers by 9–169.0%
Chargers by 1–819.4%
Level after regulation2.4%
Chiefs by 1–825.9%
Chiefs by 9–1620.5%
Chiefs by 17+18.1%

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 +5.7 points to the Chargers: the final margin was Chargers by 6, without the luck Chargers by 0.3. 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, 34 yds made · 92% expected
  • T. Vizcaino, 24 yds made · 97% expected
  • Extra point missed · 94% expected
  • Extra point missed · 94% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Chargers 8 for 50 yards, Chiefs 6 for 56 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 half toward luck; pre-snap fouls, which repeat, don’t count. How calls are valued

WhenFlagWin probability for
Q1 12:57 Face Mask on the Chiefs (L'Jarius Sneed), 7 yards +2% LAC +0.6 pts
Q1 5:36 Defensive Holding on the Chargers (Kyzir White), 5 yards 0% KC +0.3 pts
Q1 2:58 Low Block on the Chiefs (Clyde Edwards-Helaire), 15 yards +4% LAC +1.3 pts
Q2 3:07 Illegal Shift on the Chargers (Jalen Guyton), 5 yards, wiping out the play · pre-snap +6% KC +2.5 pts
Q2 0:41 False Start on the Chiefs, 5 yards · pre-snap +2% LAC +0.6 pts
Q3 11:33 Defensive Holding on the Chargers, 5 yards +2% KC +0.4 pts
Q3 5:39 Unnecessary Roughness on the Chargers (Kyzir White), 15 yards +8% KC +1.7 pts
Q3 5:19 Illegal Use of Hands on the Chiefs, 10 yards, wiping out the play +16% LAC +2.8 pts
Q4 4:04 False Start on the Chargers, 5 yards · pre-snap +4% KC +0.9 pts
Q4 3:23 Defensive Pass Interference on the Chiefs (L'Jarius Sneed), 4 yards +8% LAC +2.1 pts
Q4 2:35 Illegal Shift on the Chargers (Jared Cook), 5 yards, wiping out the play · pre-snap +17% KC +1.8 pts
Q4 0:48 Defensive Pass Interference on the Chiefs (Deandre Baker), 15 yards +14% LAC +2.4 pts
Q4 0:48 False Start on the Chargers, 5 yards · pre-snap +1% LAC +0.7 pts
Q4 0:24 Defensive Holding on the Chargers, 5 yards +3% KC +0.9 pts

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

When it happened

Chiefs’ chance of winning

As low as 0% and as high as 71%. 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 Chargers were.
#WhenWhat happenedWin probability forNext drive
1 Q1 2:58 The Chiefs fumbled and the Chargers recoveredFumble bounces · loose balls are close to 50/50Low Block on the Chiefs (Clyde Edwards-Helaire), 15 yardsJudgment calls · 1 flag in 688 snaps before, position avg 1 per 773 +14% LAC KC: Turnover
2 Q3 6:20 The Chiefs converted 3rd & 103rd & 4th downs · 31% expected +12% KC KC: Touchdown
3 Q3 5:19 Illegal Use of Hands on the Chiefs, 10 yards, wiping out the playJudgment calls +16% LAC LAC: Touchdown
4 Q4 15:00 The Chargers converted 4th & 43rd & 4th downs · 52% expected +12% LAC LAC: Touchdown
5 Q4 2:35 Illegal Shift on the Chargers (Jared Cook), 5 yards, wiping out the playPre-snap flags · 7 flags in 1155 snaps before, position avg 1 per 269 +17% KC KC: Turnover
6 Q4 2:24 The Chargers were stopped on 3rd & 63rd & 4th downs · 35% expected +10% KC LAC: Field goal
7 Q4 1:04 The Chargers converted 3rd & 23rd & 4th downs · 66% expected +11% LAC LAC: Touchdown
8 Q4 0:48 Defensive Pass Interference on the Chiefs (Deandre Baker), 15 yardsJudgment calls · 8 flags in 1081 snaps before, position avg 1 per 213False Start on the Chargers, 5 yardsPre-snap flags +15% 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.

  • Frank Clark (KC DE), out · 0.8 pts
  • Charvarius Ward (KC CB), out · 0.6 pts
  • Justin Jones (LAC DT), 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

Chargers 59% · Chiefs 41%

Final margin
Chargers by 6
Luck in points
5.7 for the Chargers
Luck-adjusted margin
Chargers by 0.3
Replay with same day's form
Chargers 33% · Chiefs 67% unchanged: why
How much of each is luck?

0% treats it as skill, 100% as pure luck. The tick is our fit.

What counts

None by default: our tests measured no carryover after a lucky break. Slide it up to count a break for more than its own swing. 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 3 2021 games · Chargers · Chiefs

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