luckadjusted

Week 4 2021 · October 3, 2021

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

Chiefs at Eagles, Week 4 2021: who deserved to win?

The Chiefs beat the Eagles 42–30, and it was no fluke: replayed with the way both teams actually played, the Chiefs win 9 of 10.

Before kickoff the Chiefs were 71% favorites. The biggest swing (Q3, 7:16 left): Offensive Pass Interference on the Eagles (JJ Arcega-Whiteside), 10 yards, wiping out the play, worth 20 points of win probability to the Chiefs.

Final

Kansas City Chiefs 42
Philadelphia Eagles 30

October 3, 2021 · Lincoln Financial Field · Closing line: Chiefs −7.5

Luck index +5 Chiefs about even · −5 Eagles

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 9, Eagles win 1.

  1. 1 KC 38 PHI 7
  2. 2 KC 34 PHI 10
  3. 3 KC 38 PHI 17
  4. 4 KC 33 PHI 16
  5. 5 KC 31 PHI 17
  6. 6 KC 33 PHI 22
  7. 7 KC 43 PHI 34
  8. 8 KC 27 PHI 21
  9. 9 KC 10 PHI 7
  10. 10 KC 23 PHI 28

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 95% of them, Eagles 5%, counting the 1% still level after regulation as half each. The line is what actually happened: Chiefs by 12.

Show as a table
Final margin in the replaysShare of replays
Chiefs by 17+58.0%
Chiefs by 9–1622.6%
Chiefs by 1–814.1%
Level after regulation0.6%
Eagles by 1–83.4%
Eagles by 9–161.2%
Eagles by 17+0.2%

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 +10.1 points to the Chiefs: the final margin was Chiefs by 12, without the luck Chiefs by 1.9. 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.

  • J. Elliott, 29 yds made · 96% expected
  • J. Elliott, 25 yds made · 98% expected
  • J. Elliott, 31 yds made · 95% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Chiefs 7 for 46 yards, Eagles 9 for 49 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 toward luck, pre-snap fouls mostly don’t. How calls are valued

WhenFlagWin probability for
Q1 10:25 Encroachment on the Eagles (Josh Sweat), 6 yards · pre-snap +4% KC +0.7 pts
Q1 3:03 Offensive Holding on the Eagles, 10 yards, wiping out the play +6% KC +1.7 pts
Q1 1:13 Illegal Contact on the Eagles, 5 yards, wiping out the play +3% KC +1.4 pts
Q2 15:00 Illegal Formation on the Chiefs, 5 yards · pre-snap +4% PHI +1.1 pts
Q2 14:28 Delay of Game on the Chiefs, 5 yards · pre-snap +2% PHI +0.9 pts
Q2 11:11 Offensive Holding on the Chiefs, 10 yards, wiping out the play +7% PHI +2.0 pts
Q2 4:31 Face Mask on the Chiefs, 3 yards, wiping out the play +4% KC +1.1 pts
Q2 1:15 Roughing the Passer on the Eagles (Derek Barnett), 3 yards +1% KC +0.5 pts
Q3 12:09 False Start on the Eagles (Zach Ertz), 5 yards · pre-snap +1% KC +0.5 pts
Q3 8:34 Delay of Game on the Eagles, 5 yards · pre-snap +3% KC +0.8 pts
Q3 7:18 Defensive Offside on the Chiefs, 3 yards · pre-snap +1% PHI +0.1 pts
Q3 7:16 Offensive Pass Interference on the Eagles (JJ Arcega-Whiteside), 10 yards, wiping out the play +20% KC +4.1 pts
Q4 15:00 Unnecessary Roughness on the Chiefs (Alex Okafor), 15 yards +4% PHI +1.1 pts
Q4 9:57 Neutral Zone Infraction on the Eagles (Josh Sweat), 5 yards · pre-snap +1% KC +1.1 pts
Q4 5:23 Illegal Touch Pass on the Eagles (DeVonta Smith), 0 yards 0% KC 0.0 pts
Q4 2:46 Illegal Formation on the Chiefs (Byron Pringle), 5 yards, wiping out the play · pre-snap 0% PHI +0.9 pts

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

When it happened

Eagles’ chance of winning

As low as 0% and as high as 66%. 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 Eagles were ahead in it, below while the Chiefs were.
#WhenWhat happenedWin probability forNext drive
1 Q1 3:46 The Eagles converted 4th & 23rd & 4th downs · 61% expected +10% PHI PHI: Touchdown
2 Q2 14:14 The Chiefs converted 3rd & 123rd & 4th downs · 29% expected +8% KC KC: Touchdown
3 Q2 11:11 Offensive Holding on the Chiefs, 10 yards, wiping out the playJudgment calls +7% PHI PHI: Field goal
4 Q2 9:29 The Chiefs converted 3rd & 63rd & 4th downs · 35% expected +8% KC KC: Touchdown
5 Q2 3:38 J. Elliott made 25-yard field goalKicks · 98% expected for him +6% KC PHI: End of half
6 Q3 12:18 The Chiefs were stopped on 3rd & 93rd & 4th downs · 35% expected +8% PHI KC: Touchdown
7 Q3 7:16 Offensive Pass Interference on the Eagles (JJ Arcega-Whiteside), 10 yards, wiping out the playJudgment calls · 2 flags in 735 snaps before, position avg 1 per 399 +20% KC KC: Touchdown
8 Q4 12:46 The Eagles converted 3rd & 73rd & 4th downs · 28% expected +9% PHI PHI: 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.

  • Lane Johnson (PHI T), out · 1.2 pts
  • Jordan Mailata (PHI T), out · 0.8 pts
  • Brandon Graham (PHI DE), out (IR) · 0.5 pts
  • Isaac Seumalo (PHI OL), out (IR) · 0.4 pts
  • Brandon Brooks (PHI G), out (IR) · 0.3 pts
  • Isaac Seumalo (PHI G), out (IR) · 0.3 pts
  • K'Von Wallace (PHI SS), out (IR) · 0.1 pts
  • Frank Clark (KC DE), out · 0.8 pts
  • Charvarius Ward (KC CB), out · 0.6 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 74% · Eagles 26%

Final margin
Chiefs by 12
Luck in points
10.1 for the Chiefs
Luck-adjusted margin
Chiefs by 1.9
Replay with same day's form
Chiefs 95% · Eagles 5% 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 4 2021 games · Chiefs · Eagles

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