luckadjusted

Week 2 2021 · September 19, 2021

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

Bills at Dolphins, Week 2 2021: who deserved to win?

The Bills beat the Dolphins 35–0, and it was no fluke: replayed with the way both teams actually played, the Bills win 9 of 10.

Before kickoff the Bills were 60% favorites.

Final

Buffalo Bills 35
Miami Dolphins 0

September 19, 2021 · Hard Rock Stadium · Closing line: Bills −3.5

Luck index +5 Bills about even · −5 Dolphins

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 9, Dolphins win 1.

  1. 1 BUF 43 MIA 6
  2. 2 BUF 34 MIA 6
  3. 3 BUF 33 MIA 10
  4. 4 BUF 30 MIA 10
  5. 5 BUF 32 MIA 16
  6. 6 BUF 33 MIA 20
  7. 7 BUF 27 MIA 17
  8. 8 BUF 20 MIA 14
  9. 9 BUF 23 MIA 20
  10. 10 BUF 14 MIA 22

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

Bills win 95% of them, Dolphins 5%, counting the 1% still level after regulation as half each. The line is what actually happened: Bills by 35.

Show as a table
Final margin in the replaysShare of replays
Bills by 17+66.6%
Bills by 9–1619.4%
Bills by 1–88.5%
Level after regulation0.9%
Dolphins by 1–83.6%
Dolphins by 9–161.0%
Dolphins by 17+0.1%

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 +8.0 points to the Bills: the final margin was Bills by 35, without the luck Bills by 27. Luck shares are the fitted ones (how much of each kind is luck).

Penalties: Bills 6 for 53 yards, Dolphins 9 for 83 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
Q1 11:55 Ineligible Downfield Pass on the Dolphins, 5 yards, wiping out the play +5% BUF +2.0 pts
Q1 3:16 False Start on the Dolphins (Durham Smythe), 5 yards · pre-snap +1% BUF +0.8 pts
Q1 2:49 Taunting on the Bills, 15 yards +3% MIA +1.8 pts
Q1 1:02 Offensive Holding on the Dolphins (Brandon Jones), 10 yards +2% BUF +0.9 pts
Q2 11:50 Defensive Offside on the Bills (Vernon Butler), 5 yards, wiping out the play · pre-snap 0% BUF +0.1 pts
Q2 8:06 False Start on the Bills, 5 yards · pre-snap +1% MIA +0.7 pts
Q2 3:21 Offensive Holding on the Dolphins, 10 yards, wiping out the play +3% BUF +1.3 pts
Q2 1:33 Intentional Grounding on the Dolphins (Jacoby Brissett), 10 yards +2% BUF +0.7 pts
Q2 0:54 Offensive Holding on the Bills, 8 yards +1% MIA +0.7 pts
Q2 0:46 False Start on the Bills, 4 yards · pre-snap +2% MIA +0.1 pts
Q3 13:54 Face Mask on the Dolphins, 15 yards +2% BUF +1.8 pts
Q3 9:43 False Start on the Dolphins, 5 yards · pre-snap +1% BUF +0.9 pts
Q3 7:49 Unnecessary Roughness on the Dolphins (Brandon Jones), 15 yards +1% BUF +1.7 pts
Q4 14:55 Unnecessary Roughness on the Dolphins (Emmanuel Ogbah), 8 yards 0% BUF +1.5 pts
Q4 4:27 Defensive Pass Interference on the Bills (Siran Neal), 16 yards 0% MIA +1.7 pts

Bills penalties, every game · Dolphins penalties, every game · All teams, 2021

When it happened

Dolphins’ chance of winning

As low as 0% and as high as 55%. 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 Dolphins were ahead in it, below while the Bills were.
#WhenWhat happenedWin probability forNext drive
1 Q1 11:55 Ineligible Downfield Pass on the Dolphins, 5 yards, wiping out the playJudgment calls +5% BUF BUF: Touchdown
2 Q1 9:27 The Bills converted 3rd & 53rd & 4th downs · 42% expected +4% BUF BUF: Touchdown
3 Q2 12:42 The Dolphins converted 3rd & 73rd & 4th downs · 29% expected +4% MIA MIA: Turnover
4 Q2 9:58 The Dolphins were stopped on 3rd & 63rd & 4th downs · 32% expectedThe Dolphins fumbled and the Bills recoveredFumble bounces · loose balls are close to 50/50 +6% BUF MIA: Turnover on downs
5 Q2 8:27 The Bills converted 3rd & 73rd & 4th downs · 35% expected +4% BUF BUF: Turnover
6 Q2 5:43 The Dolphins were stopped on 4th & 23rd & 4th downs · 55% expected +4% BUF MIA: Punt
7 Q2 1:41 The Dolphins converted 3rd & 83rd & 4th downs · 27% expected +4% MIA MIA: Punt
8 Q2 0:38 The Dolphins fumbled and the Bills recoveredFumble bounces · loose balls are close to 50/50 +4% BUF MIA: End of half

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.

  • Raekwon Davis (MIA DT), out (IR) · 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

Bills 100% · Dolphins 0%

Final margin
Bills by 35
Luck in points
8.0 for the Bills
Luck-adjusted margin
Bills by 27.0
Replay with same day's form
Bills 95% · Dolphins 5% 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 2 2021 games · Bills · Dolphins

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