Week 4 2021 · October 3, 2021
No FTN charting for this game (drops and interception-worthy throws are not modelled).
Seahawks at 49ers, Week 4 2021: who deserved to win?
The Seahawks stole one. They beat the 49ers 28–21, but replayed with the way both teams actually played, the 49ers win 9 of 10. Luck ran their way: fumble bounces alone were worth 6.3 points to the Seahawks.
The Seahawks won on an off day: their offense played far below its usual level. In a fresh game against the 49ers they would win 40% of the time; with this day’s form, 8%. The numbers
Before kickoff the 49ers were 57% favorites. The biggest swing (Q1, 5:26 left): the 49ers were stopped on 3rd & 3, worth 9 points of win probability to the Seahawks.
Final
 Seattle Seahawks | 28 |
|---|---|
 San Francisco 49ers | 21 |
Replay with same day's form
Luck index +92 Seahawks very lucky · −92 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. Seahawks win 1, 49ers win 9.
- 1 SEA 41 SF 34
- 2 SEA 26 SF 28
- 3 SEA 30 SF 36
- 4 SEA 17 SF 26
- 5 SEA 32 SF 44
- 6 SEA 21 SF 37
- 7 SEA 24 SF 42
- 8 SEA 14 SF 36
- 9 SEA 16 SF 44
- 10 SEA 10 SF 47
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.
The Seahawks won on an off day
Their offense played far below its usual level. In a fresh game against the 49ers they would win 40% of the time; with this day’s form, 8%.
Same teams, fresh game
Replay with same day's form
32 points apart for the Seahawks: the gap is how differently this game went from what the two teams usually are.
| Unit | This game | Usual level | Better or worse than usual |
|---|---|---|---|
| Seahawks offenseEPA per play gained | +0.02 | +0.16 | worse by 0.14 |
| Seahawks defenseEPA per play allowed | +0.16 | +0.13 | worse by 0.04 |
| 49ers offenseEPA per play gained | +0.16 | +0.15 | better by 0.01 |
| 49ers defenseEPA per play allowed | +0.02 | +0.07 | better by 0.05 |
EPA (expected points added) per play on competitive snaps, turnovers left out because they are valued as luck. Usual level: the team’s earlier games this season plus half of last season, pulled toward the league average. One team’s defense and the other team’s offense are the same snaps, so one game can’t fully say whose day it was; it shows how far this one was from both teams’ norms.
How 4,000 replays ended
Seahawks win 8% of them, 49ers 92%, counting the 1% still level after regulation as half each. The line is what actually happened: Seahawks by 7.
Show as a table
| Final margin in the replays | Share of replays |
|---|---|
| Seahawks by 17+ | 0.4% |
| Seahawks by 9–16 | 1.8% |
| Seahawks by 1–8 | 5.8% |
| Level after regulation | 0.7% |
| 49ers by 1–8 | 11.6% |
| 49ers by 9–16 | 19.6% |
| 49ers by 17+ | 60.2% |
Where the luck was
Take the luck out
The final margin was Seahawks by 7. Remove the luck, one kind at a time, and it becomes 49ers by 10.4.
The kicks
How likely each kicker was to make that kick (his own record, the distance and the weather), and what happened.
- M. Wishnowsky, 41 yds missed · 88% expected
- Extra point missed · 88% expected
When it happened
49ers’ chance of winning
As low as 0% and as high as 85%. Numbers mark the biggest luck moments, listed below.
| # | When | What happened | Win probability for | Next drive |
|---|---|---|---|---|
| 1 | Q1 5:26 | The 49ers were stopped on 3rd & 33rd & 4th downs · 54% expected | +9% SEA | SF: Missed field goal |
| 2 | Q1 5:16 | The Seahawks fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 | +6% SEA | SEA: Punt |
| 3 | Q1 4:29 | The Seahawks were stopped on 3rd & 73rd & 4th downs · 34% expected | +5% SF | SEA: Punt |
| 4 | Q2 13:36 | M. Wishnowsky missed 41-yard field goalKicks · 88% expected for him | +6% SEA | SF: Punt |
| 5 | Q2 2:44 | The Seahawks converted 3rd & 13rd & 4th downs · 73% expected | +6% SEA | SEA: Touchdown |
| 6 | Q2 0:47 | The Seahawks fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 | +8% SEA | SEA: End of half |
| 7 | Q3 5:22 | The 49ers fumbled and the Seahawks recoveredFumble bounces · loose balls are close to 50/50 | +7% SEA | SF: Touchdown |
| 8 | Q4 13:01 | Defensive Pass Interference on the 49ers (Dre Kirkpatrick), 23 yardsJudgment calls · 9 flags in 1098 snaps before, position avg 1 per 213 | +5% SEA | SEA: 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.
- Josh Norman (SF CB), out · 0.6 pts
- K'Waun Williams (SF CB), out · 0.4 pts
- Jason Verrett (SF CB), out (IR) · 0.4 pts
- Dre Greenlaw (SF LB), out (IR) · 0.3 pts
- Tarvarius Moore (SF DB), out (IR) · 0.3 pts
- Richie James (SF WR), out (IR) · 0.3 pts
- Justin Skule (SF OL), out (IR) · 0.1 pts
- Elijah Mitchell (SF RB), out · 0.1 pts
- Gerald Everett (SEA TE), out (IR) · 0.7 pts
- Brandon Shell (SEA T), out · 0.7 pts
- Ethan Pocic (SEA G/C), out (IR) · 0.2 pts
- Benson Mayowa (SEA LB), 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
Seahawks 5% · 49ers 95%
- Final margin
- Seahawks by 7
- Luck in points
- 17.4 for the Seahawks
- Luck-adjusted margin
- 49ers by 10.4
- Replay with same day's form
- Seahawks 8% · 49ers 92% 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 4 2021 games · 
Seahawks · 
49ers
More from Week 4 2021
- Jaguars at Bengals CIN 24–21 · replay 42% for the winner
- Panthers at Cowboys DAL 36–28 · replay 78% for the winner
- Browns at Vikings CLE 14–7 · replay 63% for the winner
- Lions at Bears CHI 24–14 · replay 72% for the winner
- Texans at Bills BUF 40–0 · replay 98% for the winner
- Colts at Dolphins IND 27–17 · replay 88% for the winner
- Chiefs at Eagles KC 42–30 · replay 95% for the winner
- Giants at Saints NYG 27–21 · replay 17% for the winner
- Titans at Jets NYJ 27–24 · replay 30% for the winner
- Washington at Falcons WAS 34–30 · replay 70% for the winner
- Cardinals at Rams ARI 37–20 · replay 71% for the winner
- Ravens at Broncos BAL 23–7 · replay 89% for the winner
- Steelers at Packers GB 27–17 · replay 86% for the winner
- Buccaneers at Patriots TB 19–17 · replay 77% for the winner
- Raiders at Chargers LAC 28–14 · replay 78% for the winner