luckadjusted
NFL Week 9 · 2026

Week 4 2019 · September 29, 2019

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

Chiefs at Lions, Week 4 2019: who deserved to win?

The Chiefs beat the Lions 34–30, and the replays back it up: with the way both teams actually played, the Chiefs win 8 of 10. The Lions had the bounces: kicks alone were worth 26 points of win probability to the Lions.

Before kickoff the Chiefs were 71% favorites. The game turned on a luck play (Q3, 9:31 left): Return touchdown by the Chiefs, worth 68 points of win probability to the Chiefs.

Final

Kansas City Chiefs 34
Detroit Lions 30

September 29, 2019 · Ford Field · Closing line: Chiefs −7.5

Luck index +16 Chiefs about even · −16 Lions

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, Lions win 2.

  1. 1 KC 48 DET 14
  2. 2 KC 52 DET 28
  3. 3 KC 30 DET 10
  4. 4 KC 54 DET 38
  5. 5 KC 33 DET 21
  6. 6 KC 37 DET 29
  7. 7 KC 38 DET 33
  8. 8 KC 36 DET 34
  9. 9 KC 13 DET 16
  10. 10 KC 34 DET 48

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 84% of them, Lions 16%, counting the 2% 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+44.7%
Chiefs by 9–1620.8%
Chiefs by 1–818.2%
Level after regulation1.9%
Lions by 1–88.4%
Lions by 9–163.9%
Lions by 17+2.0%

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 +6.5 points to the Lions: the final margin was Chiefs by 4, without the luck Chiefs by 10.5. 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.

  • M. Prater, 25 yds made · 98% expected
  • H. Butker, 36 yds missed · 93% expected
  • H. Butker, 23 yds made · 98% expected
  • M. Prater, 48 yds made · 76% expected
  • H. Butker, 44 yds made · 84% expected
  • M. Prater, 53 yds made · 69% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Chiefs 7 for 51 yards, Lions 8 for 48 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 5:39 Face Mask on the Chiefs, 15 yards +5% DET +1.8 pts
Q1 5:03 Defensive Holding on the Chiefs, 5 yards 0% DET +0.2 pts
Q1 1:01 Defensive Too Many Men on Field on the Lions, 5 yards · pre-snap 0% KC +0.2 pts
Q1 0:05 Illegal Use of Hands on the Lions (Jarrad Davis), 5 yards +1% KC +0.8 pts
Q2 10:13 Defensive Holding on the Chiefs (Damien Wilson), 5 yards, wiping out the play +7% DET +2.4 pts
Q2 9:22 Offensive Holding on the Lions, 10 yards +1% KC +1.2 pts
Q2 6:02 Unnecessary Roughness on the Lions, 3 yards +2% KC +0.7 pts
Q2 1:08 False Start on the Lions, 4 yards · pre-snap +3% KC +0.5 pts
Q3 9:49 Face Mask on the Chiefs, 1 yard +2% DET +0.5 pts
Q3 6:24 Neutral Zone Infraction on the Chiefs (Jordan Lucas), 5 yards · pre-snap +2% DET +0.6 pts
Q3 6:19 Offensive Holding on the Chiefs (Jordan Lucas), 10 yards +4% DET +0.8 pts
Q3 0:15 Roughing the Passer on the Lions (Devon Kennard), 15 yards +10% KC +1.6 pts
Q4 12:12 Neutral Zone Infraction on the Lions, 1 yard · pre-snap +3% KC +0.3 pts
Q4 9:25 Illegal Block Above the Waist on the Chiefs (Tanoh Kpassagnon), 10 yards +6% DET +0.9 pts
Q4 1:20 Defensive Holding on the Lions, 5 yards +17% KC +0.9 pts

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

When it happened

Lions’ chance of winning

As low as 0% and as high as 81%. 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 Lions were ahead in it, below while the Chiefs were.
#WhenWhat happenedWin probability forNext drive
1 Q1 5:43 H. Butker missed a 36-yard field goalKicks · 93% expected for him +11% DET KC: Field goal
2 Q3 9:31 The game turned hereThe Lions fumbled and the Chiefs recoveredFumble bounces · loose balls are close to 50/50Return touchdown by the ChiefsSpecial teams +68% KC DET: Field goal
3 Q3 6:24 M. Prater made a 53-yard field goalKicks · 69% expected for him, 2 of 3 from 45+ beforeNeutral Zone Infraction on the Chiefs (Jordan Lucas), 5 yardsPre-snap flags · 1 flag in 34 snaps before, position avg 1 per 441 +9% DET DET: Touchdown
4 Q3 1:14 The Lions converted 3rd & 93rd & 4th downs · 23% expected +11% DET DET: Touchdown
5 Q3 0:15 Roughing the Passer on the Lions (Devon Kennard), 15 yardsJudgment calls · 0 flags in 219 snaps before, position avg 1 per 393 +10% KC KC: Touchdown
6 Q4 1:55 The Chiefs converted 4th & 83rd & 4th downs · 35% expected +14% KC KC: Touchdown
7 Q4 1:20 Defensive Holding on the Lions, 5 yardsJudgment calls +17% KC KC: Touchdown
8 Q4 0:02 The Lions were stopped on 3rd & 43rd & 4th downs · 47% expected +19% KC –

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.

  • Darius Slay (DET CB), out · 1.1 pts
  • Danny Amendola (DET WR), out · 0.4 pts
  • Tyreek Hill (KC WR), out · 1.5 pts
  • Eric Fisher (KC T), out · 1.3 pts
  • Damien Williams (KC RB), 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 91% · Lions 9%

Final margin
Chiefs by 4
Luck in points
6.5 for the Lions
Luck-adjusted margin
Chiefs by 10.5
Replay with same day's form
Chiefs 84% · Lions 16% 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 4 2019 games · Chiefs · Lions

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