luckadjusted

Week 17 2020 · January 3, 2021

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

Chargers at Chiefs, Week 17 2020: who deserved to win?

The Chargers beat the Chiefs 38–21 and were the better team on the day: replayed with the same form, they win 8 of 10. The Chiefs had the bounces: fumble bounces alone were worth 1.6 points to the Chiefs.

Before kickoff the Chargers were 70% favorites. The biggest swing (Q1, 13:36 left): the Chiefs converted 3rd & 9, worth 13 points of win probability to the Chiefs.

Final

Los Angeles Chargers 38
Kansas City Chiefs 21

January 3, 2021 · Arrowhead Stadium · Closing line: Chargers −7

Luck index +24 Chargers about even · −24 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 8, Chiefs win 2.

  1. 1 LAC 37 KC 10
  2. 2 LAC 37 KC 17
  3. 3 LAC 37 KC 21
  4. 4 LAC 40 KC 27
  5. 5 LAC 27 KC 17
  6. 6 LAC 28 KC 21
  7. 7 LAC 23 KC 19
  8. 8 LAC 23 KC 21
  9. 9 LAC 17 KC 20
  10. 10 LAC 29 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

Chargers win 76% of them, Chiefs 24%, counting the 4% still level after regulation as half each. The line is what actually happened: Chargers by 17.

Show as a table
Final margin in the replaysShare of replays
Chargers by 17+22.9%
Chargers by 9–1623.7%
Chargers by 1–826.4%
Level after regulation3.8%
Chiefs by 1–814.6%
Chiefs by 9–166.0%
Chiefs by 17+2.6%

Where the luck was

Take the luck out

The final margin was Chargers by 17. Remove the luck, one kind at a time, and it becomes Chargers by 5.6.

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).

When it happened

Chiefs’ chance of winning

As low as 0% and as high as 73%. 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 13:36 The Chiefs converted 3rd & 93rd & 4th downs · 33% expected +13% KC KC: Touchdown
2 Q2 15:00 The Chiefs converted 3rd & 73rd & 4th downs · 38% expected +7% KC KC: Touchdown
3 Q2 8:52 Defensive Offside on the Chargers, 5 yards, wiping out the playPre-snap flags +7% KC KC: Punt
4 Q2 7:00 The Chargers converted 3rd & 123rd & 4th downs · 28% expected +8% LAC LAC: Turnover on downs
5 Q2 6:04 The Chargers converted 3rd & 103rd & 4th downs · 32% expected +8% LAC LAC: Turnover on downs
6 Q2 1:56 The Chargers were stopped on 4th & 23rd & 4th downs · 56% expected +11% KC LAC: Touchdown
7 Q2 0:09 The Chiefs fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 +6% KC KC: Turnover on downs
8 Q3 4:30 The Chiefs were stopped on 3rd & 13rd & 4th downs · 77% expected +8% LAC KC: 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.

  • Patrick Mahomes (KC QB), out, replaced by c.henne · 8.8 pts
  • Tyreek Hill (KC WR), out · 1.6 pts
  • Tyrann Mathieu (KC S), out · 0.8 pts
  • Sammy Watkins (KC WR), out · 0.7 pts
  • Mike Remmers (KC T), out · 0.6 pts
  • Anthony Hitchens (KC LB), out (IR) · 0.3 pts
  • Clyde Edwards-Helaire (KC RB), out · 0.1 pts
  • Sam Tevi (LAC T), out · 1.1 pts
  • Hunter Henry (LAC TE), out (IR) · 1.0 pts
  • Joey Bosa (LAC DE), out · 1.0 pts
  • Keenan Allen (LAC WR), out (IR) · 1.0 pts
  • Casey Hayward (LAC CB), out (IR) · 1.0 pts
  • Melvin Ingram (LAC DE), out (IR) · 0.8 pts
  • Bryan Bulaga (LAC T), out · 0.6 pts
  • Rayshawn Jenkins (LAC S), out · 0.4 pts
  • Kyzir White (LAC LB), out (IR) · 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 99% · Chiefs 1%

Final margin
Chargers by 17
Luck in points
11.5 for the Chargers
Luck-adjusted margin
Chargers by 5.5
Replay with same day's form
Chargers 76% · Chiefs 24% 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 17 2020 games · Chargers · Chiefs

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