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 48 PHI 17
  2. 2 KC 34 PHI 10
  3. 3 KC 28 PHI 7
  4. 4 KC 30 PHI 13
  5. 5 KC 31 PHI 17
  6. 6 KC 27 PHI 16
  7. 7 KC 23 PHI 14
  8. 8 KC 28 PHI 22
  9. 9 KC 16 PHI 13
  10. 10 KC 12 PHI 17

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

Take the luck out

The final margin was Chiefs by 12. Remove the luck, one kind at a time, and it becomes Chiefs by 1.9.

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).

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.

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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