luckadjusted
NFL Week 9 · 2026

Week 13 2024 · December 1, 2024

49ers at Bills, Week 13 2024: who deserved to win?

The Bills beat the 49ers 35–10, and the replays back it up: with the way both teams actually played, the Bills win 10 of 10.

Before kickoff the Bills were 68% favorites. The biggest swing (Q2, 11:33 left): Illegal Contact on the Bills (Rasul Douglas), 5 yards, wiping out the play, worth 19 points of win probability to the 49ers.

Final

San Francisco 49ers 10
Buffalo Bills 35

December 1, 2024 · New Era Field · Closing line: Bills −6.5

Luck index +3 Bills about even · −3 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. 49ers win 0, Bills win 10.

  1. 1 SF 34 BUF 37
  2. 2 SF 13 BUF 20
  3. 3 SF 10 BUF 20
  4. 4 SF 24 BUF 38
  5. 5 SF 28 BUF 45
  6. 6 SF 10 BUF 28
  7. 7 SF 17 BUF 38
  8. 8 SF 16 BUF 41
  9. 9 SF 13 BUF 41
  10. 10 SF 7 BUF 40

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 2% of them, Bills 98%, counting the 1% still level after regulation as half each. The line is what actually happened: Bills by 25.

Show as a table
Final margin in the replaysShare of replays
49ers by 17+0.2%
49ers by 9–160.3%
49ers by 1–81.9%
Level after regulation0.7%
Bills by 1–86.7%
Bills by 9–1618.6%
Bills by 17+71.5%

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 +14.8 points to the Bills: the final margin was Bills by 25, without the luck Bills by 10.2. 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, 33 yds made · 92% expected
  • J. Moody, 45 yds missed · 74% expected
  • J. Moody, 55 yds missed · 55% expected
  • T. Bass, 49 yds missed · 65% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: 49ers 2 for 10 yards, Bills 5 for 35 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 13:35 False Start on the Bills (Dawson Knox), 5 yards · pre-snap +1% SF +0.7 pts
Q1 6:50 Illegal Contact on the 49ers, 5 yards +7% BUF +1.7 pts
Q2 11:33 Illegal Contact on the Bills (Rasul Douglas), 5 yards, wiping out the play +19% SF +4.0 pts
Q2 10:35 Delay of Game on the 49ers, 5 yards · pre-snap +2% BUF +0.5 pts
Q3 12:15 Encroachment on the Bills (Von Miller), 5 yards · pre-snap +1% BUF +0.5 pts
Q4 12:22 Offensive Holding on the Bills, 10 yards 0% SF +1.5 pts
Q4 8:12 Offensive Holding on the Bills (Cole Bishop), 10 yards 0% SF +0.9 pts

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

When it happened

Bills’ chance of winning

As low as 38% and as high as 100%. 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 Bills were ahead in it, below while the 49ers were.
#WhenWhat happenedWin probability forNext drive
1 Q1 11:05 The 49ers converted 3rd & 13rd & 4th downs · 75% expected +4% SF SF: Field goal
2 Q1 7:47 The 49ers were stopped on 3rd & 73rd & 4th downs · 35% expected +4% BUF SF: Field goal
3 Q1 6:50 Illegal Contact on the 49ers, 5 yardsJudgment calls +7% BUF BUF: Touchdown
4 Q1 2:57 The Bills converted 3rd & 63rd & 4th downs · 44% expected +5% BUF BUF: Touchdown
5 Q2 11:33 Illegal Contact on the Bills (Rasul Douglas), 5 yards, wiping out the playJudgment calls · 34 flags in 5452 snaps before, position avg 1 per 215 +19% SF SF: Missed field goal
6 Q2 8:52 J. Moody missed a 45-yard field goalKicks · 74% expected for him, 10 of 16 from 45+ before +9% BUF SF: Punt
7 Q2 6:33 The 49ers converted 3rd & 43rd & 4th downs · 46% expected +2% SF SF: Punt
8 Q3 11:57 The 49ers fumbled and the Bills recoveredFumble bounces · loose balls are close to 50/50 +3% BUF SF: Punt

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.

  • Dalton Kincaid (BUF TE), out · 0.8 pts
  • Keon Coleman (BUF WR), out · 0.6 pts
  • Dawuane Smoot (BUF DE), out (IR) · 0.2 pts
  • Brandon Aiyuk (SF WR), out (IR) · 1.4 pts
  • Trent Williams (SF T), out · 1.2 pts
  • Nick Bosa (SF DE), out · 1.1 pts
  • Deommodore Lenoir (SF CB), out · 0.7 pts
  • Aaron Banks (SF G), out · 0.4 pts
  • Jordan Elliott (SF DT), out · 0.2 pts
  • Mitch Wishnowsky (SF P), 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

49ers 1% · Bills 99%

Final margin
Bills by 25
Luck in points
14.8 for the Bills
Luck-adjusted margin
Bills by 10.2
Replay with same day's form
49ers 2% · Bills 98% 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 13 2024 games · 49ers · Bills

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