luckadjusted

Week 15 2021 · December 19, 2021

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

Falcons at 49ers, Week 15 2021: who deserved to win?

The 49ers beat the Falcons 31–13, and it was no fluke: replayed with the way both teams actually played, the 49ers win 9 of 10. The Falcons had the bounces: injuries alone were worth 2.1 points to the Falcons.

Before kickoff the 49ers were 76% favorites. The biggest swing (Q1, 12:32 left): the Falcons were stopped on 4th & 1, worth 12 points of win probability to the 49ers.

Final

Atlanta Falcons 13
San Francisco 49ers 31

December 19, 2021 · Levi's Stadium · Closing line: 49ers −9.5

Luck index +11 49ers about even · −11 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 1, 49ers win 9.

  1. 1 ATL 30 SF 24
  2. 2 ATL 17 SF 20
  3. 3 ATL 14 SF 20
  4. 4 ATL 16 SF 24
  5. 5 ATL 13 SF 23
  6. 6 ATL 21 SF 34
  7. 7 ATL 27 SF 43
  8. 8 ATL 20 SF 38
  9. 9 ATL 19 SF 41
  10. 10 ATL 0 SF 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 11% of them, 49ers 89%, counting the 2% still level after regulation as half each. The line is what actually happened: 49ers by 18.

Show as a table
Final margin in the replaysShare of replays
Falcons by 17+0.5%
Falcons by 9–162.1%
Falcons by 1–88.2%
Level after regulation1.7%
49ers by 1–819.3%
49ers by 9–1624.4%
49ers by 17+43.8%

Where the luck was

Take the luck out

The final margin was 49ers by 18. Remove the luck, one kind at a time, and it becomes 49ers by 14.6.

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.

  • Y. Koo, 48 yds made · 81% expected
  • R. Gould, 30 yds made · 96% expected
  • Y. Koo, 22 yds made · 100% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

49ers’ chance of winning

As low as 34% 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 49ers were ahead in it, below while the Falcons were.
#WhenWhat happenedWin probability forNext drive
1 Q1 15:00 The 49ers fumbled and the Falcons recoveredFumble bounces · loose balls are close to 50/50 +5% ATL SF: Punt
2 Q1 12:32 The Falcons were stopped on 4th & 13rd & 4th downs · 67% expected +12% SF ATL: Field goal
3 Q1 9:37 False Start on the Falcons, 5 yardsPre-snap flags +6% SF SF: Field goal
4 Q1 9:15 The Falcons converted 3rd & 63rd & 4th downs · 38% expected +9% ATL ATL: Field goal
5 Q1 0:42 The Falcons converted 3rd & 23rd & 4th downs · 61% expectedDefensive Too Many Men on Field on the 49ers, 5 yardsPre-snap flags +7% ATL ATL: Punt
6 Q2 4:50 Roughing the Passer on the 49ers (Arden Key), 15 yardsJudgment calls · 8 flags in 1039 snaps before, position avg 1 per 266 +6% ATL ATL: Touchdown
7 Q2 2:00 Defensive Pass Interference on the Falcons (Fabian Moreau), 14 yardsJudgment calls · 10 flags in 1908 snaps before, position avg 1 per 213 +12% SF SF: Touchdown
8 Q3 13:28 The Falcons were stopped on 3rd & 83rd & 4th downs · 33% expectedThe Falcons fumbled and the 49ers recoveredFumble bounces · loose balls are close to 50/50 +11% SF ATL: Field goal

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.

  • Mike McGlinchey (SF T), out (IR) · 0.9 pts
  • Emmanuel Moseley (SF CB), out (IR) · 0.6 pts
  • Mohamed Sanu (SF WR), out (IR) · 0.4 pts
  • Azeez Al-Shaair (SF LB), out · 0.3 pts
  • Elijah Mitchell (SF RB), out · 0.1 pts
  • Erik Harris (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 0% · 49ers 100%

Final margin
49ers by 18
Luck in points
3.3 for the 49ers
Luck-adjusted margin
49ers by 14.7
Replay with same day's form
Falcons 11% · 49ers 89% 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 15 2021 games · Falcons · 49ers

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