luckadjusted

Week 10 2021 · November 15, 2021

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

Rams at 49ers, Week 10 2021: who deserved to win?

The 49ers beat the Rams 31–10, but it was a coin flip: replayed with the way both teams played, the 49ers win 5 of 10. Luck ran their way: 3rd & 4th downs alone were worth 3.8 points to the 49ers.

Before kickoff the Rams were 60% favorites. The biggest swing (Q1, 0:58 left): Return touchdown by the 49ers, worth 17 points of win probability to the 49ers.

Final

Los Angeles Rams 10
San Francisco 49ers 31

November 15, 2021 · Levi's Stadium · Closing line: Rams −3.5

Luck index +51 49ers lucky · −51 Rams

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. Rams win 5, 49ers win 5.

  1. 1 LA 45 SF 23
  2. 2 LA 30 SF 16
  3. 3 LA 26 SF 16
  4. 4 LA 20 SF 16
  5. 5 LA 27 SF 24
  6. 6 LA 14 SF 16
  7. 7 LA 17 SF 22
  8. 8 LA 17 SF 26
  9. 9 LA 19 SF 34
  10. 10 LA 10 SF 32

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

Rams win 51% of them, 49ers 49%, counting the 5% still level after regulation as half each. The line is what actually happened: 49ers by 21.

Show as a table
Final margin in the replaysShare of replays
Rams by 17+9.9%
Rams by 9–1614.4%
Rams by 1–823.7%
Level after regulation5.5%
49ers by 1–823.1%
49ers by 9–1614.1%
49ers by 17+9.3%

Where the luck was

Take the luck out

The final margin was 49ers by 21. Remove the luck, one kind at a time, and it becomes 49ers by 20.7.

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.

  • R. Gould, 50 yds made · 71% expected
  • M. Gay, 37 yds made · 92% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

49ers’ chance of winning

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 Rams were.
#WhenWhat happenedWin probability forNext drive
1 Q1 10:26 The 49ers converted 3rd & 63rd & 4th downs · 35% expected +6% SF SF: Touchdown
2 Q1 7:51 Defensive Offside on the Rams (Terrell Lewis), 5 yardsPre-snap flags · 3 flags in 459 snaps before, position avg 1 per 409 +3% SF SF: Touchdown
3 Q1 7:02 The 49ers converted 3rd & 13rd & 4th downs · 71% expected +3% SF SF: Touchdown
4 Q1 5:07 The 49ers converted 3rd & 43rd & 4th downs · 43% expected +5% SF SF: Touchdown
5 Q1 1:59 The 49ers converted 3rd & 63rd & 4th downs · 28% expected +6% SF SF: Touchdown
6 Q1 0:58 The Rams were stopped on 3rd & 113rd & 4th downs · 25% expectedReturn touchdown by the 49ersSpecial teams +17% SF LA: Touchdown
7 Q2 13:20 The Rams converted 3rd & 93rd & 4th downs · 22% expected +5% LA LA: Touchdown
8 Q2 8:23 The 49ers converted 3rd & 73rd & 4th downs · 32% expected +5% SF SF: 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.

  • Mike McGlinchey (SF T), out (IR) · 0.9 pts
  • Jaquiski Tartt (SF SS), out (IR) · 0.4 pts
  • Javon Kinlaw (SF DT), out (IR) · 0.3 pts
  • Robert Woods (LA WR), out · 1.0 pts
  • Donte Deayon (LA CB), out · 0.6 pts
  • Justin Hollins (LA LB), out (IR) · 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

Rams 0% · 49ers 100%

Final margin
49ers by 21
Luck in points
0.3 for the 49ers
Luck-adjusted margin
49ers by 20.7
Replay with same day's form
Rams 51% · 49ers 49% 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 10 2021 games · Rams · 49ers

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