luckadjusted

Week 17 2021 · January 2, 2022

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

Falcons at Bills, Week 17 2021: who deserved to win?

The Bills beat the Falcons 29–15 and were the better team on the day: replayed with the same form, they win 7 of 10.

Before kickoff the Bills were 85% favorites. The biggest swing (Q3, 14:14 left): the Bills were stopped on 3rd & 7, worth 15 points of win probability to the Falcons.

Final

Atlanta Falcons 15
Buffalo Bills 29

January 2, 2022 · New Era Field · Closing line: Bills −14

Luck index +25 Bills lucky · −25 Falcons

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. Falcons win 3, Bills win 7.

  1. 1 ATL 28 BUF 14
  2. 2 ATL 27 BUF 20
  3. 3 ATL 21 BUF 19
  4. 4 ATL 28 BUF 30
  5. 5 ATL 34 BUF 38
  6. 6 ATL 17 BUF 24
  7. 7 ATL 17 BUF 27
  8. 8 ATL 17 BUF 31
  9. 9 ATL 3 BUF 20
  10. 10 ATL 9 BUF 31

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

Falcons win 25% of them, Bills 75%, counting the 4% still level after regulation as half each. The line is what actually happened: Bills by 14.

Show as a table
Final margin in the replaysShare of replays
Falcons by 17+2.5%
Falcons by 9–166.0%
Falcons by 1–815.4%
Level after regulation4.4%
Bills by 1–826.5%
Bills by 9–1623.2%
Bills by 17+22.1%

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 +7.8 points to the Bills: the final margin was Bills by 14, without the luck Bills by 6.2. 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.

  • Y. Koo, 28 yds made · 97% expected
  • Y. Koo, 24 yds made · 99% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Falcons 4 for 27 yards, Bills 7 for 47 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 11:04 Offside on Free Kick on the Bills (Taiwan Jones), 5 yards · pre-snap +1% ATL +0.2 pts
Q1 4:31 Ineligible Downfield Pass on the Bills, 5 yards 0% ATL +0.7 pts
Q1 3:29 Defensive Pass Interference on the Falcons (AJ Terrell), 2 yards +7% BUF +3.8 pts
Q2 13:48 Neutral Zone Infraction on the Bills, 5 yards · pre-snap +2% ATL +1.0 pts
Q2 12:08 Roughing the Passer on the Bills (Ed Oliver), 15 yards +2% ATL +1.0 pts
Q2 0:33 Defensive Offside on the Bills (Jerry Hughes), 5 yards · pre-snap +2% ATL +0.5 pts
Q3 12:40 Delay of Game on the Falcons, 5 yards · pre-snap 0% BUF +1.1 pts
Q3 3:54 Illegal Forward Pass on the Falcons (Matt Ryan), 5 yards +1% BUF +0.4 pts
Q3 0:07 Illegal Shift on the Bills (Gabriel Davis), 5 yards · pre-snap +2% ATL +1.3 pts
Q4 9:41 Defensive Pass Interference on the Bills (Taron Johnson), 7 yards +1% ATL +1.8 pts
Q4 6:14 Taunting on the Falcons (Matt Ryan), 15 yards +1% BUF +1.1 pts

Falcons 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 Falcons were.
#WhenWhat happenedWin probability forNext drive
1 Q1 11:18 The Bills fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 +6% BUF BUF: Touchdown
2 Q1 10:11 The Falcons were stopped on 3rd & 73rd & 4th downs · 33% expected +7% BUF ATL: Punt
3 Q1 7:10 The Bills converted 3rd & 103rd & 4th downs · 31% expected +6% BUF BUF: Touchdown
4 Q1 3:29 Defensive Pass Interference on the Falcons (AJ Terrell), 2 yardsJudgment calls · 7 flags in 1926 snaps before, position avg 1 per 213 +7% BUF BUF: Touchdown
5 Q2 3:31 The Bills were stopped on 3rd & 83rd & 4th downs · 28% expected +9% ATL BUF: Turnover
6 Q2 0:23 The Falcons converted 3rd & 103rd & 4th downs · 27% expected +9% ATL ATL: Field goal
7 Q2 0:02 Y. Koo made 24-yard field goalKicks · 99% expected for him +6% BUF ATL: Punt
8 Q3 14:14 The Bills were stopped on 3rd & 73rd & 4th downs · 38% expected +15% ATL 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.

  • Tre'Davious White (BUF CB), out (IR) · 1.1 pts
  • Emmanuel Sanders (BUF WR), out · 0.8 pts
  • Ike Boettger (BUF G), out (IR) · 0.3 pts
  • Fabian Moreau (ATL CB), out · 0.5 pts
  • Erik Harris (ATL FS), out (IR) · 0.3 pts
  • Tajae Sharpe (ATL WR), out (IR) · 0.3 pts
  • Jaylinn Hawkins (ATL FS), 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

Falcons 19% · Bills 81%

Final margin
Bills by 14
Luck in points
7.8 for the Bills
Luck-adjusted margin
Bills by 6.2
Replay with same day's form
Falcons 25% · Bills 75% 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 2021 games · Falcons · Bills

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