luckadjusted

Week 17 2020 · January 3, 2021

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

Seahawks vs 49ers, Week 17 2020: who deserved to win?

The Seahawks beat the 49ers 26–23 and were the better team on the day: replayed with the same form, they win 8 of 10. The 49ers had the bounces: kicks alone were worth 15 points of win probability to the 49ers.

Before kickoff the Seahawks were 70% favorites. The biggest swing (Q4, 2:26 left): the Seahawks converted 4th & 4, worth 22 points of win probability to the Seahawks.

Final

Seattle Seahawks 26
San Francisco 49ers 23

January 3, 2021 · State Farm Stadium · Closing line: Seahawks −7

Luck index +24 Seahawks about even · −24 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 8, 49ers win 2.

  1. 1 SEA 48 SF 20
  2. 2 SEA 29 SF 9
  3. 3 SEA 40 SF 23
  4. 4 SEA 34 SF 20
  5. 5 SEA 34 SF 23
  6. 6 SEA 33 SF 26
  7. 7 SEA 17 SF 12
  8. 8 SEA 26 SF 24
  9. 9 SEA 23 SF 26
  10. 10 SEA 10 SF 24

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

Seahawks win 76% of them, 49ers 24%, counting the 4% still level after regulation as half each. The line is what actually happened: Seahawks by 3.

Show as a table
Final margin in the replaysShare of replays
Seahawks by 17+28.7%
Seahawks by 9–1620.1%
Seahawks by 1–823.2%
Level after regulation4.0%
49ers by 1–813.3%
49ers by 9–167.1%
49ers by 17+3.5%

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 +6.0 points to the Seahawks: the final margin was Seahawks by 3, without the luck 49ers by 3. 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. Myers, 36 yds made · 93% expected
  • J. Myers, 30 yds made · 97% expected
  • T. Vizcaino, 36 yds made · 93% expected
  • T. Vizcaino, 47 yds made · 79% expected
  • T. Vizcaino, 33 yds made · 95% expected
  • Extra point missed · 93% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Seahawks 4 for 35 yards, 49ers 2 for 25 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 toward luck, pre-snap fouls mostly don’t. How calls are valued

WhenFlagWin probability for
Q2 8:17 Illegal Block Above the Waist on the Seahawks (Freddie Swain), 10 yards +3% SF +0.9 pts
Q2 3:49 Offensive Holding on the 49ers, 10 yards +9% SEA +2.0 pts
Q2 0:25 False Start on the Seahawks (Tyler Lockett), 5 yards · pre-snap +2% SF +0.2 pts
Q3 14:15 Roughing the Passer on the Seahawks (L.J. Collier), 15 yards +5% SF +1.9 pts
Q4 13:44 Unnecessary Roughness on the 49ers (Dontae Johnson), 15 yards +3% SEA +1.9 pts
Q4 1:54 False Start on the Seahawks, 5 yards · pre-snap 0% SEA +0.8 pts

Seahawks 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 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 Seahawks were.
#WhenWhat happenedWin probability forNext drive
1 Q2 8:47 The 49ers were stopped on 3rd & 33rd & 4th downs · 51% expected +8% SEA SF: Punt
2 Q2 5:12 The 49ers converted 3rd & 143rd & 4th downs · 22% expected +13% SF SF: Field goal
3 Q2 3:49 Offensive Holding on the 49ers, 10 yardsJudgment calls +9% SEA SEA: End of half
4 Q3 7:05 The 49ers were stopped on 3rd & 43rd & 4th downs · 37% expected +10% SEA SF: Field goal
5 Q3 3:52 The 49ers converted 3rd & 83rd & 4th downs · 31% expected +8% SF SF: Touchdown
6 Q4 2:28 The Seahawks were stopped on 3rd & 43rd & 4th downs · 38% expected +10% SF SEA: Touchdown
7 Q4 2:26 The Seahawks converted 4th & 43rd & 4th downs · 37% expected +22% SEA SEA: Touchdown
8 Q4 2:16 The 49ers fumbled and the Seahawks recoveredFumble bounces · loose balls are close to 50/50 +12% SEA SF: 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.

  • Richard Sherman (SF CB), out · 1.6 pts
  • Nick Mullens (SF QB), out (IR), replaced by c.beathard · 1.5 pts
  • Brandon Aiyuk (SF WR), out · 1.5 pts
  • Trent Williams (SF T), out (IR) · 1.2 pts
  • Deebo Samuel (SF WR), out · 1.2 pts
  • K'Waun Williams (SF CB), out · 0.4 pts
  • Dre Greenlaw (SF LB), out · 0.3 pts
  • Robbie Gould (SF K), out (IR) · 0.3 pts
  • Javon Kinlaw (SF DT), out · 0.3 pts
  • Taybor Pepper (SF LS), out (IR) · 0.1 pts
  • Brandon Shell (SEA T), out (IR) · 0.7 pts
  • Greg Olsen (SEA TE), out · 0.6 pts
  • Mike Iupati (SEA G), out · 0.4 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 74% · 49ers 26%

Final margin
Seahawks by 3
Luck in points
6.0 for the Seahawks
Luck-adjusted margin
49ers by 3.0
Replay with same day's form
Seahawks 76% · 49ers 24% 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 17 2020 games · Seahawks · 49ers

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