luckadjusted
NFL Week 9 · 2026

Week 17 2019 · December 29, 2019

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

Chargers at Chiefs, Week 17 2019: who deserved to win?

The Chiefs beat the Chargers 31–21, and the replays back it up: with the way both teams actually played, the Chiefs win 8 of 10.

Before kickoff the Chiefs were 77% favorites. The biggest swing (Q3, 13:14 left): Return touchdown by the Chiefs, worth 23 points of win probability to the Chiefs.

Final

Los Angeles Chargers 21
Kansas City Chiefs 31

December 29, 2019 · Arrowhead Stadium · Closing line: Chiefs −10

Luck index +19 Chiefs about even · −19 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. Chargers win 2, Chiefs win 8.

  1. 1 LAC 27 KC 17
  2. 2 LAC 23 KC 20
  3. 3 LAC 24 KC 26
  4. 4 LAC 12 KC 17
  5. 5 LAC 30 KC 38
  6. 6 LAC 6 KC 17
  7. 7 LAC 14 KC 27
  8. 8 LAC 17 KC 33
  9. 9 LAC 24 KC 44
  10. 10 LAC 7 KC 35

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 19% of them, Chiefs 81%, counting the 2% still level after regulation as half each. The line is what actually happened: Chiefs by 10.

Show as a table
Final margin in the replaysShare of replays
Chargers by 17+1.9%
Chargers by 9–165.5%
Chargers by 1–810.8%
Level after regulation1.9%
Chiefs by 1–827.6%
Chiefs by 9–1622.0%
Chiefs by 17+30.3%

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 +1.5 points to the Chargers: the final margin was Chiefs by 10, without the luck Chiefs by 11.5. Luck shares are the fitted ones (how much of each kind is luck).

Penalties: Chargers 8 for 40 yards, Chiefs 5 for 39 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 7:10 Defensive Offside on the Chargers (Uchenna Nwosu), 5 yards · pre-snap +2% KC +1.2 pts
Q1 5:53 Defensive Offside on the Chargers (Joey Bosa), 5 yards, wiping out the play · pre-snap +14% KC +4.6 pts
Q2 6:14 Illegal Use of Hands on the Chiefs, 10 yards, wiping out the play +10% LAC +2.1 pts
Q2 5:25 False Start on the Chargers, 5 yards · pre-snap +2% KC +0.7 pts
Q2 2:00 False Start on the Chargers, 5 yards · pre-snap +1% KC +0.5 pts
Q3 8:39 Ineligible Downfield Pass on the Chargers, 5 yards +3% KC +0.7 pts
Q3 3:18 Lowering the Head to Initiate Contact on the Chiefs (Armani Watts), 15 yards +7% LAC +1.5 pts
Q4 15:00 False Start on the Chiefs (Sammy Watkins), 4 yards · pre-snap +1% LAC +0.3 pts
Q4 11:55 False Start on the Chargers (Hunter Henry), 5 yards · pre-snap +2% KC +0.6 pts
Q4 10:09 Defensive Holding on the Chiefs, 5 yards +1% LAC +0.4 pts
Q4 9:57 Defensive Pass Interference on the Chiefs (Kendall Fuller), 5 yards +2% LAC +0.7 pts
Q4 7:38 False Start on the Chargers, 5 yards · pre-snap +1% KC +0.7 pts
Q4 2:47 Defensive Holding on the Chargers (Brandon Mebane), 5 yards +1% KC +0.9 pts

Chargers penalties, every game · Chiefs penalties, every game · All teams, 2019

When it happened

Chiefs’ chance of winning

As low as 40% and as high as 100%. 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 5:53 Defensive Offside on the Chargers (Joey Bosa), 5 yards, wiping out the playPre-snap flags · 3 flags in 806 snaps before, position avg 1 per 249 +14% KC KC: Field goal
2 Q2 11:49 The Chargers converted 3rd & 103rd & 4th downs · 30% expected +7% LAC LAC: Touchdown
3 Q2 7:39 The Chiefs converted 3rd & 63rd & 4th downs · 41% expected +9% KC KC: Punt
4 Q2 6:14 Illegal Use of Hands on the Chiefs, 10 yards, wiping out the playJudgment calls +10% LAC LAC: Punt
5 Q2 3:07 The Chiefs converted 3rd & 73rd & 4th downs · 38% expected +9% KC KC: Touchdown
6 Q3 13:14 Return touchdown by the ChiefsSpecial teams +23% KC KC: Touchdown
7 Q3 9:24 The Chargers converted 3rd & 93rd & 4th downs · 32% expected +8% LAC LAC: Punt
8 Q3 0:33 The Chargers were stopped on 4th & 13rd & 4th downs · 70% expected +10% KC 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.

  • Emmanuel Ogbah (KC DE), out (IR) · 0.7 pts
  • Martinas Rankin (KC T), out (IR) · 0.4 pts
  • Alex Okafor (KC DE), out (IR) · 0.4 pts
  • Andrew Wylie (KC G), out · 0.3 pts
  • Cameron Erving (KC T), out · 0.3 pts
  • Russell Okung (LAC T), out · 0.7 pts
  • Roderic Teamer (LAC CB), 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 0% · Chiefs 100%

Final margin
Chiefs by 10
Luck in points
1.5 for the Chargers
Luck-adjusted margin
Chiefs by 11.5
Replay with same day's form
Chargers 19% · Chiefs 81% 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 17 2019 games · Chargers · Chiefs

More from Week 17 2019