luckadjusted

Week 15 2023 · December 17, 2023

49ers at Cardinals, Week 15 2023: who deserved to win?

The 49ers beat the Cardinals 45–29, and it was no fluke: replayed with the way both teams actually played, the 49ers win 10 of 10. The Cardinals had the bounces: fumble bounces alone were worth 6.3 points to the Cardinals.

Before kickoff the 49ers were 82% favorites. The biggest swing (Q1, 4:33 left): Return touchdown by the 49ers, worth 40 points of win probability to the 49ers.

Final

San Francisco 49ers 45
Arizona Cardinals 29

December 17, 2023 · State Farm Stadium · Closing line: 49ers −12.5

Luck index +1 49ers about even · −1 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 10, Cardinals win 0.

  1. 1 SF 43 ARI 3
  2. 2 SF 41 ARI 7
  3. 3 SF 45 ARI 17
  4. 4 SF 43 ARI 19
  5. 5 SF 35 ARI 14
  6. 6 SF 25 ARI 7
  7. 7 SF 25 ARI 10
  8. 8 SF 19 ARI 7
  9. 9 SF 17 ARI 9
  10. 10 SF 17 ARI 14

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 99% of them, Cardinals 1%. The line is what actually happened: 49ers by 16.

Show as a table
Final margin in the replaysShare of replays
49ers by 17+86.7%
49ers by 9–169.8%
49ers by 1–82.6%
Level after regulation0.2%
Cardinals by 1–80.7%
Cardinals by 9–160.1%
Cardinals by 17+0.0%

Where the luck was

Take the luck out

The final margin was 49ers by 16. Remove the luck, one kind at a time, and it becomes 49ers by 22.9.

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.

  • M. Prater, 58 yds made · 59% expected
  • M. Prater, 43 yds made · 82% expected
  • M. Prater, 28 yds made · 97% expected
  • J. Moody, 43 yds made · 82% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

Cardinals’ chance of winning

As low as 0% and as high as 70%. 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 4:35 The Cardinals were stopped on 3rd & 33rd & 4th downs · 50% expectedE. Demercado dropped a catchable passDrops · 0 drops on 12 catchable balls before this +10% SF ARI: Opp touchdown
2 Q1 4:33 The Cardinals were stopped on 4th & 33rd & 4th downs · 50% expectedThe Cardinals threw an interception-worthy pass, and it was pickedInterceptions · 49% expected to stay out of the defense's handsReturn touchdown by the 49ersSpecial teams +40% SF ARI: Field goal
3 Q2 14:15 M. Prater made 58-yard field goalKicks · 59% expected for him, 44 of 61 from 45+ before +7% ARI ARI: Field goal
4 Q2 11:29 The Cardinals fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 +7% ARI ARI: Field goal
5 Q2 10:15 The Cardinals converted 4th & 13rd & 4th downs · 72% expected +9% ARI ARI: Field goal
6 Q2 7:32 The Cardinals fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 +8% ARI ARI: Field goal
7 Q2 4:13 Roughing the Passer on the Cardinals, 15 yardsJudgment calls +5% SF SF: Touchdown
8 Q3 14:14 The 49ers converted 3rd & 113rd & 4th downs · 31% expected +8% SF SF: 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.

  • Kyzir White (ARI LB), out (IR) · 0.4 pts
  • Carter O'Donnell (ARI T), out · 0.4 pts
  • Dennis Daley (ARI T), out · 0.3 pts
  • Talanoa Hufanga (SF SS), out (IR) · 0.7 pts
  • Javon Hargrave (SF DT), out · 0.4 pts
  • Arik Armstead (SF DT), out · 0.3 pts
  • Spencer Burford (SF G), 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 100% · Cardinals 0%

Final margin
49ers by 16
Luck in points
6.9 for the Cardinals
Luck-adjusted margin
49ers by 22.9
Replay with same day's form
49ers 99% · Cardinals 1% 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; injuries from snap counts and injury reports.

Methodology and validation · All Week 15 2023 games · 49ers · Cardinals

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