luckadjusted

Week 13 2021 · December 5, 2021

No FTN charting for this game (drops and interception-worthy throws are not modelled).

49ers at Seahawks, Week 13 2021: who deserved to win?

The Seahawks stole one. They beat the 49ers 30–23, but replayed with the way both teams actually played, the 49ers win 10 of 10. Luck ran their way: judgment calls alone were worth 6.5 points to the Seahawks.

The Seahawks won on an off day: they played far below what the matchup promised. In a fresh game against the 49ers they would win 42% of the time; with this day’s form, 2%. The numbers

Before kickoff the 49ers were 59% favorites. The biggest swing (Q1, 13:22 left): the Seahawks converted 4th & 6, worth 24 points of win probability to the Seahawks.

Final

San Francisco 49ers 23
Seattle Seahawks 30

December 5, 2021 · Lumen Field · Closing line: 49ers −3

Luck index +98 Seahawks very lucky · −98 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 10, Seahawks win 0.

  1. 1 SF 46 SEA 7
  2. 2 SF 43 SEA 10
  3. 3 SF 37 SEA 10
  4. 4 SF 41 SEA 17
  5. 5 SF 31 SEA 10
  6. 6 SF 28 SEA 10
  7. 7 SF 27 SEA 12
  8. 8 SF 36 SEA 24
  9. 9 SF 27 SEA 19
  10. 10 SF 37 SEA 33

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.

The Seahawks won on an off day

They played far below what the matchup promised. In a fresh game against the 49ers they would win 42% of the time; with this day’s form, 2%.

40 points apart for the Seahawks: the gap is how differently this game went from what the two teams usually are.

UnitThis gameUsual levelBetter or worse than usual
49ers offenseEPA per play gained +0.20 +0.15 better by 0.05
49ers defenseEPA per play allowed +0.17 +0.08 worse by 0.08
Seahawks offenseEPA per play gained +0.17 +0.11 better by 0.06
Seahawks defenseEPA per play allowed +0.20 +0.12 worse by 0.09

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

49ers win 98% of them, Seahawks 2%, 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 replaysShare of replays
49ers by 17+78.4%
49ers by 9–1613.2%
49ers by 1–85.9%
Level after regulation0.6%
Seahawks by 1–81.5%
Seahawks by 9–160.4%
Seahawks by 17+0.2%

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 3.5.

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. Myers, 56 yds missed · 63% expected
  • R. Gould, 50 yds made · 70% expected
  • Extra point missed · 93% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

Seahawks’ chance of winning

As low as 19% 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 Seahawks were ahead in it, below while the 49ers were.
#WhenWhat happenedWin probability forNext drive
1 Q1 13:22 The Seahawks converted 4th & 63rd & 4th downs · 32% expected +24% SEA SEA: Touchdown
2 Q3 15:00 The 49ers fumbled and the Seahawks recoveredFumble bounces · loose balls are close to 50/50 +10% SEA SF: Safety
3 Q3 12:02 The Seahawks were stopped on 3rd & 43rd & 4th downs · 33% expected +18% SF SEA: Punt
4 Q3 5:29 The 49ers converted 3rd & 53rd & 4th downs · 40% expected +9% SF SF: Turnover
5 Q3 2:34 The Seahawks converted 3rd & 63rd & 4th downs · 33% expected +13% SEA SEA: Touchdown
6 Q4 3:14 Offensive Holding on the 49ers, 10 yards, wiping out the playJudgment calls +10% SEA SEA: End of game
7 Q4 2:00 Illegal Block Above the Waist on the 49ers (Trent Sherfield), 10 yardsJudgment calls · 3 flags in 1050 snaps before, position avg 1 per 399 +10% SEA SEA: End of game
8 Q4 0:22 The 49ers were stopped on 4th & 33rd & 4th downs · 42% expected +11% SEA –

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.

  • Damien Lewis (SEA G), out · 0.5 pts
  • Tre Brown (SEA DB), out (IR) · 0.2 pts
  • Deebo Samuel (SF WR), out · 1.1 pts
  • Mike McGlinchey (SF T), out (IR) · 0.9 pts
  • Fred Warner (SF LB), out · 0.8 pts
  • Mohamed Sanu (SF WR), out (IR) · 0.4 pts
  • Javon Kinlaw (SF DT), out (IR) · 0.3 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 55% · Seahawks 45%

Final margin
Seahawks by 7
Luck in points
10.5 for the Seahawks
Luck-adjusted margin
49ers by 3.5
Replay with same day's form
49ers 98% · Seahawks 2% 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 (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 2021 games · 49ers · Seahawks

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