luckadjusted

Week 17 2024 · December 30, 2024

Lions at 49ers, Week 17 2024: who deserved to win?

The Lions beat the 49ers 40–34, but the 49ers played well enough to win it: they take 6 of 10 replays with the same day's form. Luck ran their way: kicks alone were worth 6.9 points to the Lions.

Before kickoff the Lions were 62% favorites. The biggest swing (Q2, 10:17 left): the Lions converted 3rd & 12, worth 17 points of win probability to the Lions.

Final

Detroit Lions 40
San Francisco 49ers 34

December 30, 2024 · Levi's Stadium · Closing line: Lions −4

Luck index +62 Lions very lucky · −62 49ers

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. Lions win 4, 49ers win 6.

  1. 1 DET 38 SF 17
  2. 2 DET 32 SF 20
  3. 3 DET 27 SF 20
  4. 4 DET 19 SF 17
  5. 5 DET 19 SF 21
  6. 6 DET 38 SF 42
  7. 7 DET 21 SF 29
  8. 8 DET 17 SF 30
  9. 9 DET 17 SF 36
  10. 10 DET 20 SF 47

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

Lions win 38% of them, 49ers 62%, counting the 3% still level after regulation as half each. The line is what actually happened: Lions by 6.

Show as a table
Final margin in the replaysShare of replays
Lions by 17+6.7%
Lions by 9–1610.9%
Lions by 1–820.4%
Level after regulation2.7%
49ers by 1–826.7%
49ers by 9–1616.9%
49ers by 17+15.7%

Where the luck was

Take the luck out

The final margin was Lions by 6. Remove the luck, one kind at a time, and it becomes 49ers by 6.5.

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. Moody, 51 yds missed · 66% expected
  • J. Bates, 57 yds made · 59% expected
  • J. Moody, 58 yds missed · 54% expected
  • J. Bates, 42 yds made · 84% expected
  • Extra point missed · 93% expected
  • Extra point missed · 93% expected
  • Extra point missed · 93% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

49ers’ chance of winning

As low as 0% and as high as 87%. 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 49ers were ahead in it, below while the Lions were.
#WhenWhat happenedWin probability forNext drive
1 Q2 10:17 The Lions converted 3rd & 123rd & 4th downs · 28% expected +17% DET DET: Touchdown
2 Q2 7:46 The 49ers converted 3rd & 73rd & 4th downs · 36% expected +11% SF SF: Touchdown
3 Q3 10:02 The Lions converted 3rd & 63rd & 4th downs · 34% expected +9% DET DET: Touchdown
4 Q3 5:12 The Lions were stopped on 3rd & 33rd & 4th downs · 56% expected +11% SF DET: Field goal
5 Q3 0:22 The Lions converted 4th & 43rd & 4th downs · 41% expected +14% DET DET: Touchdown
6 Q4 13:30 J. Moody missed 58-yard field goalKicks · 54% expected for him, 12 of 21 from 45+ before +13% DET SF: Turnover
7 Q4 12:03 The Lions converted 4th & 33rd & 4th downs · 55% expected +10% DET DET: Field goal
8 Q4 8:27 Ineligible Downfield Pass on the 49ers, 5 yards, wiping out the playJudgment calls +15% DET DET: 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.

  • Trent Williams (SF T), out (IR) · 1.2 pts
  • Christian McCaffrey (SF RB), out (IR) · 0.7 pts
  • Charvarius Ward (SF CB), out · 0.6 pts
  • De'Vondre Campbell (SF LB), out (IR) · 0.5 pts
  • Aaron Banks (SF G), out (IR) · 0.4 pts
  • Jaylon Moore (SF T), out (IR) · 0.3 pts
  • Mitch Wishnowsky (SF P), out (IR) · 0.2 pts
  • Carlton Davis (DET CB), out (IR) · 0.8 pts
  • Alim McNeill (DET DT), out (IR) · 0.4 pts
  • Alex Anzalone (DET LB), out (IR) · 0.3 pts
  • Malcolm Rodriguez (DET LB), out (IR) · 0.2 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

Lions 29% · 49ers 71%

Final margin
Lions by 6
Luck in points
12.5 for the Lions
Luck-adjusted margin
49ers by 6.5
Replay with same day's form
Lions 38% · 49ers 62% 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 17 2024 games · Lions · 49ers

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