luckadjusted
NFL Week 9 · 2026

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 replays call it close to a coin flip: with the way both teams played, the Lions win 5 of 10. Luck ran their way: kicks alone were worth 28 points of win probability to the Lions.

Before kickoff the Lions were 62% favorites. The biggest swing (Q4, 8:27 left): Ineligible Downfield Pass on the 49ers, 5 yards, wiping out the play, worth 15 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 +46 Lions lucky · −46 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 5, 49ers win 5.

  1. 1 DET 28 SF 7
  2. 2 DET 41 SF 28
  3. 3 DET 19 SF 10
  4. 4 DET 31 SF 26
  5. 5 DET 30 SF 27
  6. 6 DET 24 SF 26
  7. 7 DET 22 SF 27
  8. 8 DET 19 SF 28
  9. 9 DET 26 SF 40
  10. 10 DET 13 SF 34

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 54% of them, 49ers 46%, counting the 6% 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+11.3%
Lions by 9–1614.7%
Lions by 1–823.5%
Level after regulation5.7%
49ers by 1–823.3%
49ers by 9–1612.2%
49ers by 17+9.4%

Where the luck was

What the luck was worth

Every lucky and unlucky play, weighted by the moment it happened: its swing in win probability, added up by kind. A missed kick in a decided game counts for nothing; the same kick at the end of a tie game can be most of a win.

Swings add up across a game, so in one that went back and forth they can pass 100%. On the scoreboard the same luck was worth +10.1 points to the Lions: the final margin was Lions by 6, without the luck 49ers by 4.1. Luck shares are the fitted ones (how much of each kind 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 · 65% expected
  • J. Bates, 57 yds made · 62% expected
  • J. Moody, 58 yds missed · 56% expected
  • J. Bates, 42 yds made · 85% expected
  • Extra point missed · 94% expected
  • Extra point missed · 94% expected
  • Extra point missed · 94% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Lions 6 for 57 yards, 49ers 5 for 30 yards

Every accepted flag, in order, and what it did to the helped team’s chance of winning at that moment, including any play it wiped out (points on the scoreboard in grey). A flag in a decided game is worth nothing; one at the turn of a close game can be worth most of a win. Judgment calls count half toward luck; pre-snap fouls, which repeat, don’t count. How calls are valued

WhenFlagWin probability for
Q1 3:42 Defensive Holding on the Lions (Al-Quadin Muhammad), 5 yards +2% SF +0.5 pts
Q1 0:06 Encroachment on the Lions (D.J. Reader), 5 yards · pre-snap +2% SF +0.3 pts
Q2 14:53 Illegal Formation on the Lions, 5 yards · pre-snap +1% SF +0.5 pts
Q2 11:57 Offensive Holding on the Lions, 10 yards, wiping out the play +3% SF +1.5 pts
Q2 0:20 Offensive Pass Interference on the 49ers (Jacob Cowing), 10 yards, wiping out the play +8% DET +3.5 pts
Q3 9:58 Offensive Holding on the 49ers (Brayden Willis), 10 yards +2% DET +0.9 pts
Q3 4:19 Defensive Pass Interference on the Lions (Brian Branch), 17 yards +3% SF +0.6 pts
Q4 9:43 Delay of Game on the 49ers, 5 yards · pre-snap 0% DET +0.4 pts
Q4 8:27 Ineligible Downfield Pass on the 49ers, 5 yards, wiping out the play +15% DET +2.7 pts
Q4 8:01 Unnecessary Roughness on the Lions (Brian Branch), 15 yards +7% SF +0.9 pts
Q4 0:43 Kickoff Out of Bounds on the 49ers (Jake Moody), 0 yards · pre-snap 0% DET 0.0 pts

Lions penalties, every game · 49ers penalties, every game · All teams, 2024

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 · 29% expected +8% DET DET: Touchdown
2 Q2 0:20 Offensive Pass Interference on the 49ers (Jacob Cowing), 10 yards, wiping out the playJudgment calls · 0 flags in 103 snaps before, position avg 1 per 409 +8% DET DET: End of half
3 Q3 10:02 The Lions converted 3rd & 63rd & 4th downs · 35% expected +7% DET DET: Touchdown
4 Q3 9:58 The Lions’ two-point try was good3rd & 4th downs · 47% expectedOffensive Holding on the 49ers (Brayden Willis), 10 yardsJudgment calls · 2 flags in 363 snaps before, position avg 1 per 280 +8% DET DET: Field goal
5 Q3 0:22 The Lions converted 4th & 43rd & 4th downs · 43% expected +12% DET DET: Touchdown
6 Q4 13:30 J. Moody missed a 58-yard field goalKicks · 56% expected for him, 12 of 21 from 45+ before +13% DET SF: Turnover
7 Q4 8:27 Ineligible Downfield Pass on the 49ers, 5 yards, wiping out the playJudgment calls +15% DET DET: Touchdown
8 Q4 8:01 Unnecessary Roughness on the Lions (Brian Branch), 15 yardsJudgment calls · 13 flags in 1742 snaps before, position avg 1 per 462 +7% SF SF: Turnover

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 35% · 49ers 65%

Final margin
Lions by 6
Luck in points
10.1 for the Lions
Luck-adjusted margin
49ers by 4.1
Replay with same day's form
Lions 54% · 49ers 46% unchanged: why
How much of each is luck?

0% treats it as skill, 100% as pure luck. The tick is our fit.

What counts

None by default: our tests measured no carryover after a lucky break. Slide it up to count a break for more than its own swing. 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

More from Week 17 2024