luckadjusted
NFL Week 9 · 2026

Week 8 2021 · October 31, 2021

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

Dolphins at Bills, Week 8 2021: who deserved to win?

The Bills beat the Dolphins 26–11, and the replays back it up: with the way both teams actually played, the Bills win 9 of 10.

Before kickoff the Bills were 87% favorites. The biggest swing (Q1, 8:10 left): J. Sanders had a 36-yard field goal blocked, worth 10 points of win probability to the Bills.

Final

Miami Dolphins 11
Buffalo Bills 26

October 31, 2021 · New Era Field · Closing line: Bills −15

Luck index +8 Bills about even · −8 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. Dolphins win 1, Bills win 9.

  1. 1 MIA 10 BUF 3
  2. 2 MIA 6 BUF 9
  3. 3 MIA 19 BUF 25
  4. 4 MIA 17 BUF 26
  5. 5 MIA 7 BUF 18
  6. 6 MIA 19 BUF 33
  7. 7 MIA 10 BUF 27
  8. 8 MIA 10 BUF 30
  9. 9 MIA 9 BUF 33
  10. 10 MIA 6 BUF 37

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

Dolphins win 8% of them, Bills 92%, counting the 2% still level after regulation as half each. The line is what actually happened: Bills by 15.

Show as a table
Final margin in the replaysShare of replays
Dolphins by 17+0.2%
Dolphins by 9–162.2%
Dolphins by 1–85.3%
Level after regulation1.7%
Bills by 1–816.8%
Bills by 9–1623.9%
Bills by 17+49.9%

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 +2.7 points to the Bills: the final margin was Bills by 15, without the luck Bills by 12.3. 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. Sanders, 36 yds blocked · 92% expected
  • T. Bass, 57 yds made · 62% expected
  • J. Sanders, 51 yds made · 66% expected
  • T. Bass, 39 yds made · 88% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Dolphins 9 for 58 yards, Bills 9 for 80 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

WhenFlagWin probability for
Q1 6:49 False Start on the Bills (Emmanuel Sanders), 5 yards · pre-snap +2% MIA +0.4 pts
Q1 3:48 False Start on the Dolphins, 5 yards · pre-snap +2% BUF +0.8 pts
Q1 1:49 Illegal Use of Hands on the Bills (Vernon Butler), 5 yards, wiping out the play +4% MIA +1.3 pts
Q1 0:45 False Start on the Dolphins, 5 yards · pre-snap +5% BUF +0.6 pts
Q2 2:43 Illegal Shift on the Dolphins, 5 yards, wiping out the play · pre-snap +6% BUF +1.3 pts
Q2 0:53 Intentional Grounding on the Bills (Josh Allen), 15 yards +3% MIA +1.0 pts
Q2 0:39 Horse Collar Tackle on the Bills (Matt Milano), 15 yards +3% MIA +1.7 pts
Q3 12:08 Player Out of Bounds on Kick on the Bills (Taiwan Jones), 5 yards +2% MIA +0.2 pts
Q3 10:55 Illegal Use of Hands on the Dolphins (Raekwon Davis), 5 yards, wiping out the play +2% MIA +0.1 pts
Q3 10:42 Offensive Holding on the Bills, 10 yards, wiping out the play +6% MIA +2.1 pts
Q3 4:01 Defensive Pass Interference on the Dolphins (Andrew Van Ginkel), 3 yards +4% BUF +1.2 pts
Q3 3:56 Face Mask on the Dolphins (Jaelan Phillips), 15 yards +6% BUF +1.2 pts
Q3 2:12 Illegal Use of Hands on the Dolphins (Raekwon Davis), 5 yards, wiping out the play 0% BUF +0.3 pts
Q4 14:15 False Start on the Bills (Tommy Sweeney), 5 yards · pre-snap +1% MIA +0.7 pts
Q4 12:38 Defensive Offside on the Bills (Jerry Hughes), 5 yards, wiping out the play · pre-snap +2% MIA +1.2 pts
Q4 5:54 Defensive Holding on the Dolphins (Xavien Howard), 5 yards +2% BUF +1.2 pts
Q4 4:34 Low Block on the Bills, 15 yards, wiping out the play +3% MIA +1.8 pts
Q4 3:15 Offensive Holding on the Dolphins, 10 yards +1% BUF +0.5 pts

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

When it happened

Bills’ chance of winning

As low as 37% 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 Bills were ahead in it, below while the Dolphins were.
#WhenWhat happenedWin probability forNext drive
1 Q1 12:37 The Dolphins converted 3rd & 93rd & 4th downs · 29% expected +8% MIA MIA: Missed field goal
2 Q1 11:18 The Dolphins converted 3rd & 33rd & 4th downs · 52% expected +9% MIA MIA: Missed field goal
3 Q1 8:10 J. Sanders had a 36-yard field goal blockedKicks · 92% expected for him +10% BUF MIA: Punt
4 Q1 6:27 The Bills converted 3rd & 103rd & 4th downs · 30% expected +8% BUF BUF: Field goal
5 Q2 10:45 The Dolphins converted 3rd & 63rd & 4th downs · 37% expected +9% MIA MIA: Field goal
6 Q2 0:53 The Bills were stopped on 4th & 43rd & 4th downs · 49% expectedIntentional Grounding on the Bills (Josh Allen), 15 yardsJudgment calls · 7 flags in 2711 snaps before, position avg 1 per 711 +9% MIA BUF: End of half
7 Q2 0:24 The Dolphins fumbled and the Bills recoveredFumble bounces · loose balls are close to 50/50 +8% BUF MIA: Punt
8 Q3 9:48 The Bills converted 3rd & 143rd & 4th downs · 24% expected +9% 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.

  • Dawson Knox (BUF TE), out · 0.8 pts
  • Spencer Brown (BUF T), out · 0.7 pts
  • Jerome Baker (MIA LB), out · 0.4 pts
  • Greg Mancz (MIA C), out · 0.4 pts
  • Michael Deiter (MIA C), out (IR) · 0.3 pts
  • John Jenkins (MIA NT), out · 0.1 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

Dolphins 1% · Bills 99%

Final margin
Bills by 15
Luck in points
2.7 for the Bills
Luck-adjusted margin
Bills by 12.3
Replay with same day's form
Dolphins 8% · Bills 92% unchanged: why
How much of each is luck?

0% treats it as skill, 100% as pure luck. The tick is our fit.

What counts

None by default: our tests measured no carryover after a lucky break. Slide it up to count a break for more than its own swing. 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 8 2021 games · Dolphins · Bills

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