luckadjusted

Week 9 2019 · October 31, 2019

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

49ers at Cardinals, Week 9 2019: who deserved to win?

The 49ers beat the Cardinals 28–25, but it was a coin flip: replayed with the way both teams played, the 49ers win 6 of 10. Luck ran their way: 3rd & 4th downs alone were worth 4.9 points to the 49ers.

Before kickoff the 49ers were 78% favorites. The biggest swing (Q1, 0:13 left): the 49ers converted 3rd & 3, worth 12 points of win probability to the 49ers.

Final

San Francisco 49ers 28
Arizona Cardinals 25

October 31, 2019 · State Farm Stadium · Closing line: 49ers −10.5

Luck index +42 49ers lucky · −42 Cardinals

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 6, Cardinals win 4.

  1. 1 SF 24 ARI 0
  2. 2 SF 21 ARI 6
  3. 3 SF 31 ARI 20
  4. 4 SF 20 ARI 13
  5. 5 SF 20 ARI 16
  6. 6 SF 20 ARI 17
  7. 7 SF 21 ARI 23
  8. 8 SF 11 ARI 17
  9. 9 SF 23 ARI 33
  10. 10 SF 8 ARI 27

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 58% of them, Cardinals 42%, counting the 3% still level after regulation as half each. The line is what actually happened: 49ers by 3.

Show as a table
Final margin in the replaysShare of replays
49ers by 17+13.1%
49ers by 9–1616.3%
49ers by 1–827.7%
Level after regulation3.4%
Cardinals by 1–819.6%
Cardinals by 9–1613.2%
Cardinals by 17+6.8%

Where the luck was

Take the luck out

The final margin was 49ers by 3. Remove the luck, one kind at a time, and it becomes Cardinals by 2.2.

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).

When it happened

Cardinals’ chance of winning

As low as 0% and as high as 78%. 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 Cardinals were ahead in it, below while the 49ers were.
#WhenWhat happenedWin probability forNext drive
1 Q1 13:45 Horse Collar Tackle on the 49ers (Dee Ford), 15 yardsJudgment calls · 0 flags in 159 snaps before, position avg 1 per 393 +8% ARI ARI: Touchdown
2 Q1 0:13 The 49ers converted 3rd & 33rd & 4th downs · 52% expected +12% SF SF: Touchdown
3 Q2 9:05 The 49ers converted 3rd & 63rd & 4th downs · 30% expected +9% SF SF: Touchdown
4 Q3 7:47 The 49ers converted 3rd & 43rd & 4th downs · 46% expected +7% SF SF: Touchdown
5 Q4 4:53 The Cardinals’ two-point try was good3rd & 4th downs · 47% expected +6% ARI –
6 Q4 4:37 The 49ers converted 3rd & 113rd & 4th downs · 27% expected +8% SF SF: End of game
7 Q4 2:27 The 49ers converted 3rd & 33rd & 4th downs · 53% expected +6% SF SF: End of game
8 Q4 2:00 The 49ers converted 3rd & 93rd & 4th downs · 31% expectedFalse Start on the 49ers (Emmanuel Sanders), 5 yardsPre-snap flags · 2 flags in 408 snaps before, position avg 1 per 331 +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.

  • Zach Allen (ARI DE), out · 0.7 pts
  • Justin Murray (ARI T), out · 0.6 pts
  • Damiere Byrd (ARI WR), out · 0.6 pts
  • David Johnson (ARI RB), out · 0.4 pts
  • Joe Staley (SF T), out · 1.1 pts
  • Mike McGlinchey (SF T), out · 0.9 pts
  • Ahkello Witherspoon (SF CB), out · 0.5 pts
  • Marquise Goodwin (SF WR), 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

49ers 32% · Cardinals 68%

Final margin
49ers by 3
Luck in points
5.2 for the 49ers
Luck-adjusted margin
Cardinals by 2.2
Replay with same day's form
49ers 58% · Cardinals 42% 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 9 2019 games · 49ers · Cardinals

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