luckadjusted

Week 2 2021 · September 19, 2021

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

49ers at Eagles, Week 2 2021: who deserved to win?

The 49ers beat the Eagles 17–11, but it was a coin flip: replayed with the way both teams played, the 49ers win 5 of 10. Luck ran their way: kicks alone were worth 3.4 points to the 49ers.

Before kickoff the 49ers were 59% favorites. The biggest swing (Q4, 15:00 left): the 49ers converted 3rd & 7, worth 10 points of win probability to the 49ers.

Final

San Francisco 49ers 17
Philadelphia Eagles 11

September 19, 2021 · Lincoln Financial Field · Closing line: 49ers −3

Luck index +53 49ers lucky · −53 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. 49ers win 5, Eagles win 5.

  1. 1 SF 23 PHI 3
  2. 2 SF 27 PHI 13
  3. 3 SF 17 PHI 10
  4. 4 SF 17 PHI 12
  5. 5 SF 21 PHI 19
  6. 6 SF 12 PHI 14
  7. 7 SF 13 PHI 17
  8. 8 SF 17 PHI 24
  9. 9 SF 14 PHI 28
  10. 10 SF 0 PHI 21

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

49ers win 47% of them, Eagles 53%, counting the 7% still level after regulation as half each. The line is what actually happened: 49ers by 6.

Show as a table
Final margin in the replaysShare of replays
49ers by 17+8.7%
49ers by 9–1613.3%
49ers by 1–822.9%
Level after regulation6.7%
Eagles by 1–823.6%
Eagles by 9–1614.8%
Eagles by 17+9.9%

Where the luck was

Take the luck out

The final margin was 49ers by 6. Remove the luck, one kind at a time, and it becomes 49ers by 3.4.

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, 45 yds made · 74% expected
  • J. Elliott, 47 yds blocked · 70% expected
  • R. Gould, 46 yds made · 71% 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 82%. 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 49ers were.
#WhenWhat happenedWin probability forNext drive
1 Q1 6:21 The Eagles converted 3rd & 33rd & 4th downs · 51% expected +7% PHI PHI: Field goal
2 Q1 0:39 The Eagles converted 3rd & 73rd & 4th downs · 34% expected +7% PHI PHI: Missed field goal
3 Q2 10:43 The 49ers converted 4th & 13rd & 4th downs · 73% expected +8% SF SF: Punt
4 Q2 9:21 Illegal Crackback on the 49ers (Mohamed Sanu), 15 yardsJudgment calls · 1 flag in 1158 snaps before, position avg 1 per 399 +7% PHI PHI: Turnover on downs
5 Q2 4:28 The Eagles were stopped on 4th & 33rd & 4th downs · 43% expected +8% SF PHI: End of half
6 Q3 14:38 The Eagles fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 +7% PHI PHI: Punt
7 Q4 15:00 The 49ers converted 3rd & 73rd & 4th downs · 34% expected +10% SF SF: Touchdown
8 Q4 2:30 The 49ers converted 3rd & 13rd & 4th downs · 73% expected +7% SF SF: End of game

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.

  • Rodney McLeod (PHI S), out · 0.4 pts
  • Jack Driscoll (PHI T), out (IR) · 0.2 pts
  • Jason Verrett (SF CB), out (IR) · 0.4 pts
  • Richie James (SF WR), out (IR) · 0.3 pts
  • Dre Greenlaw (SF LB), out (IR) · 0.3 pts
  • Tarvarius Moore (SF DB), out (IR) · 0.3 pts
  • Jordan Willis (SF DL), out (IR) · 0.1 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

49ers 65% · Eagles 35%

Final margin
49ers by 6
Luck in points
2.6 for the 49ers
Luck-adjusted margin
49ers by 3.4
Replay with same day's form
49ers 47% · Eagles 53% 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 2 2021 games · 49ers · Eagles

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