luckadjusted

Week 17 2020 · January 3, 2021

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

Dolphins at Bills, Week 17 2020: who deserved to win?

The Bills beat the Dolphins 56–26, and it was no fluke: replayed with the way both teams actually played, the Bills win 10 of 10. The Dolphins had the bounces: injuries alone were worth 2.3 points to the Dolphins.

An off day for the Dolphins: their offense and defense both played far below their usual level. In a fresh game against the Bills they would win 46% of the time; with this day’s form, 5%. The numbers

Before kickoff the Dolphins were 60% favorites.

Final

Miami Dolphins 26
Buffalo Bills 56

January 3, 2021 · New Era Field · Closing line: Dolphins −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. Dolphins win 0, Bills win 10.

  1. 1 MIA 30 BUF 33
  2. 2 MIA 29 BUF 38
  3. 3 MIA 26 BUF 37
  4. 4 MIA 23 BUF 38
  5. 5 MIA 30 BUF 48
  6. 6 MIA 24 BUF 45
  7. 7 MIA 23 BUF 47
  8. 8 MIA 19 BUF 47
  9. 9 MIA 27 BUF 60
  10. 10 MIA 12 BUF 55

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.

An off day for the Dolphins

Their offense and defense both played far below their usual level. In a fresh game against the Bills they would win 46% of the time; with this day’s form, 5%.

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

UnitThis gameUsual levelBetter or worse than usual
Dolphins offenseEPA per play gained −0.19 +0.09 worse by 0.28
Dolphins defenseEPA per play allowed +0.33 +0.13 worse by 0.21
Bills offenseEPA per play gained +0.33 +0.18 better by 0.16
Bills defenseEPA per play allowed −0.19 +0.07 better by 0.26

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

Dolphins win 5% of them, Bills 95%, counting the 1% still level after regulation as half each. The line is what actually happened: Bills by 30.

Show as a table
Final margin in the replaysShare of replays
Dolphins by 17+0.3%
Dolphins by 9–160.9%
Dolphins by 1–82.9%
Level after regulation0.7%
Bills by 1–87.5%
Bills by 9–1614.9%
Bills by 17+72.8%

Where the luck was

Take the luck out

The final margin was Bills by 30. Remove the luck, one kind at a time, and it becomes Bills by 33.1.

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. Sanders, 49 yds made · 72% expected
  • J. Sanders, 32 yds made · 95% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

Bills’ chance of winning

As low as 38% 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 8:56 The Dolphins were stopped on 3rd & 53rd & 4th downs · 39% expected +7% BUF MIA: Field goal
2 Q1 8:12 J. Sanders made 49-yard field goalKicks · 72% expected for him, 22 of 31 from 45+ before +5% MIA MIA: Punt
3 Q1 6:05 The Bills were stopped on 3rd & 83rd & 4th downs · 35% expected +4% MIA BUF: Punt
4 Q1 2:56 The Bills were stopped on 3rd & 43rd & 4th downs · 49% expected +5% MIA BUF: Punt
5 Q2 12:14 The Bills converted 3rd & 43rd & 4th downs · 40% expected +6% BUF BUF: Touchdown
6 Q2 8:31 Unnecessary Roughness on the Dolphins (Christian Wilkins), 15 yardsJudgment calls · 3 flags in 1613 snaps before, position avg 1 per 262 +5% BUF BUF: Touchdown
7 Q2 7:05 The Bills converted 3rd & 43rd & 4th downs · 49% expected +6% BUF BUF: Touchdown
8 Q3 8:28 Return touchdown by the BillsSpecial teams +4% BUF BUF: Opp 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.

  • Tre'Davious White (BUF CB), out · 1.3 pts
  • Jerry Hughes (BUF DE), out · 0.6 pts
  • Cole Beasley (BUF WR), out · 0.5 pts
  • Mario Addison (BUF DE), out · 0.4 pts
  • Elandon Roberts (MIA LB), out (IR) · 0.3 pts
  • Solomon Kindley (MIA G), 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

Dolphins 0% · Bills 100%

Final margin
Bills by 30
Luck in points
3.1 for the Dolphins
Luck-adjusted margin
Bills by 33.1
Replay with same day's form
Dolphins 5% · Bills 95% 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 · Dolphins · Bills

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