Week 13 2020 · December 7, 2020
No FTN charting for this game (drops and interception-worthy throws are not modelled).
Bills vs 49ers, Week 13 2020: who deserved to win?
The Bills beat the 49ers 34–24, but the replays call it close to a coin flip: with the way both teams played, the Bills win 5 of 10. Luck ran their way: injuries alone were worth 11 points of win probability to the Bills.
Before kickoff the 49ers were 54% favorites. The biggest swing (Q2, 8:54 left): Illegal Contact on the 49ers (Richard Sherman), 4 yards, wiping out the play, worth 16 points of win probability to the Bills.
Final
 Buffalo Bills | 34 |
|---|---|
 San Francisco 49ers | 24 |
Replay with same day's form
Luck index +48 Bills lucky · −48 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. Bills win 5, 49ers win 5.
- 1 BUF 31 SF 10
- 2 BUF 26 SF 13
- 3 BUF 28 SF 20
- 4 BUF 33 SF 28
- 5 BUF 34 SF 32
- 6 BUF 28 SF 30
- 7 BUF 30 SF 34
- 8 BUF 14 SF 22
- 9 BUF 13 SF 26
- 10 BUF 21 SF 42
Your call
Did the Bills earn it, or get lucky?
Three other ways to ask
Each answers a different question, so none of them replaces the replay above.
Before kickoff
The closing betting line, turned into a probability. What everyone knew before the game.
Same teams, fresh 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.
Only coin-flips re-rolled
Every kick, fumble bounce, drop, conversion and judgment call redrawn; everything else fixed. The narrowest view of luck.
How 4,000 replays ended
Bills win 52% of them, 49ers 48%, counting the 5% still level after regulation as half each. The line is what actually happened: Bills by 10.
Show as a table
| Final margin in the replays | Share of replays |
|---|---|
| Bills by 17+ | 11.7% |
| Bills by 9–16 | 14.8% |
| Bills by 1–8 | 22.3% |
| Level after regulation | 5.1% |
| 49ers by 1–8 | 22.2% |
| 49ers by 9–16 | 13.9% |
| 49ers by 17+ | 10.0% |
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.
The kicks
How likely each kicker was to make that kick (his own record, the distance and the weather), and what happened.
- T. Bass, 37 yds made · 92% expected
- R. Gould, 45 yds made · 79% expected
- T. Bass, 28 yds made · 97% expected
Penalties: Bills 4 for 50 yards, 49ers 7 for 43 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
| When | Flag | Win probability for |
|---|---|---|
| Q1 15:00 | Defensive Offside on the 49ers (Javon Kinlaw), 5 yards · pre-snap | 0% BUF +0.6 pts |
| Q1 7:57 | Defensive Pass Interference on the Bills, 25 yards | +7% SF +2.8 pts |
| Q2 13:37 | Defensive Holding on the 49ers (Arik Armstead), 5 yards, wiping out the play | +1% SF 0.0 pts |
| Q2 8:54 | Illegal Contact on the 49ers (Richard Sherman), 4 yards, wiping out the play | +16% BUF +4.1 pts |
| Q3 14:14 | False Start on the 49ers (Ross Dwelley), 5 yards · pre-snap | +1% BUF +0.6 pts |
| Q3 7:18 | Offensive Holding on the Bills (Cole Beasley), 10 yards | +1% SF +0.9 pts |
| Q3 6:38 | Roughing the Passer on the 49ers (Kentavius Street), 15 yards | +3% BUF +2.2 pts |
| Q3 4:46 | Offensive Holding on the Bills (Devin Singletary), 10 yards | +1% SF +1.2 pts |
| Q3 4:20 | False Start on the Bills, 5 yards · pre-snap | 0% SF +0.5 pts |
| Q4 7:05 | False Start on the 49ers (Nick Mullens), 4 yards · pre-snap | 0% BUF +1.5 pts |
| Q4 2:03 | False Start on the 49ers, 5 yards · pre-snap | 0% BUF +0.6 pts |
Bills penalties, every game · 49ers penalties, every game · All teams, 2020
When it happened
49ers’ chance of winning
As low as 0% and as high as 76%. Numbers mark the biggest luck moments, listed below.
| # | When | What happened | Win probability for | Next drive |
|---|---|---|---|---|
| 1 | Q1 9:23 | The Bills were stopped on 4th & 13rd & 4th downs · 71% expected | +13% SF | BUF: Turnover |
| 2 | Q1 7:57 | Defensive Pass Interference on the Bills, 25 yardsJudgment calls | +7% SF | SF: Turnover on downs |
| 3 | Q1 1:38 | The 49ers were stopped on 4th & 13rd & 4th downs · 70% expected | +9% BUF | SF: Touchdown |
| 4 | Q1 1:34 | The Bills fumbled and the 49ers recoveredFumble bounces · loose balls are close to 50/50 | +7% SF | BUF: Touchdown |
| 5 | Q2 8:54 | Illegal Contact on the 49ers (Richard Sherman), 4 yards, wiping out the playJudgment calls · 7 flags in 1221 snaps before, position avg 1 per 207 | +16% BUF | BUF: Touchdown |
| 6 | Q2 3:16 | The Bills converted 4th & 13rd & 4th downs · 70% expected | +4% BUF | BUF: Touchdown |
| 7 | Q4 15:00 | The Bills fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 | +5% BUF | BUF: Touchdown |
| 8 | Q4 10:44 | The Bills converted 4th & 23rd & 4th downs · 65% expected | +4% BUF | BUF: 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.
- Jimmy Garoppolo (SF QB), out (IR), replaced by n.mullens · 4.0 pts
- George Kittle (SF TE), out (IR) · 1.2 pts
- Emmanuel Moseley (SF CB), out · 0.6 pts
- Ben Garland (SF OL), out (IR) · 0.4 pts
- Jaquiski Tartt (SF S), out (IR) · 0.3 pts
- Jamar Taylor (SF DB), out (IR) · 0.2 pts
- John Brown (BUF WR), out (IR) · 0.7 pts
- Cody Ford (BUF T), out (IR) · 0.5 pts
- Cameron Lewis (BUF DB), out (IR) · 0.3 pts
- Tyler Kroft (BUF TE), out · 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
Bills 98% · 49ers 2%
- Final margin
- Bills by 10
- Luck in points
- 3.3 for the Bills
- Luck-adjusted margin
- Bills by 6.7
- Replay with same day's form
- Bills 52% · 49ers 48% unchanged: why
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 13 2020 games · 
Bills · 
49ers
More from Week 13 2020
- Bengals at Dolphins MIA 19–7 · replay 91% for the winner
- Browns at Titans CLE 41–35 · replay 64% for the winner
- Lions at Bears DET 34–30 · replay 87% for the winner
- Colts at Texans IND 26–20 · replay 78% for the winner
- Jaguars at Vikings MIN 27–24 · replay 74% for the winner
- Raiders at Jets LV 31–28 · replay 73% for the winner
- Saints at Falcons NO 21–16 · replay 55% for the winner
- Rams at Cardinals LA 38–28 · replay 91% for the winner
- Giants at Seahawks NYG 17–12 · replay 54% for the winner
- Patriots at Chargers NE 45–0 · replay 55% for the winner
- Eagles at Packers GB 30–16 · replay 90% for the winner
- Broncos at Chiefs KC 22–16 · replay 89% for the winner
- Washington at Steelers WAS 23–17 · replay 31% for the winner
- Cowboys at Ravens BAL 34–17 · replay 77% for the winner