luckadjusted

Week 16 2020 · December 26, 2020

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

49ers at Cardinals, Week 16 2020: who deserved to win?

The 49ers beat the Cardinals 20–12, and it was no fluke: replayed with the way both teams actually played, the 49ers win 9 of 10. The Cardinals had the bounces: kicks alone were worth 9.1 points to the Cardinals.

An off day for the Cardinals: their offense played far below its usual level. In a fresh game against the 49ers they would win 58% of the time; with this day’s form, 5%. The numbers

Before kickoff the Cardinals were 67% favorites. The biggest swing (Q4, 5:51 left): the Cardinals converted 4th & 1, worth 14 points of win probability to the Cardinals.

Final

San Francisco 49ers 20
Arizona Cardinals 12

December 26, 2020 · State Farm Stadium · Closing line: Cardinals −6

Luck index +5 49ers about even · −5 Cardinals

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. 49ers win 9, Cardinals win 1.

  1. 1 SF 48 ARI 10
  2. 2 SF 40 ARI 12
  3. 3 SF 37 ARI 13
  4. 4 SF 48 ARI 27
  5. 5 SF 37 ARI 20
  6. 6 SF 37 ARI 24
  7. 7 SF 17 ARI 7
  8. 8 SF 20 ARI 13
  9. 9 SF 30 ARI 27
  10. 10 SF 21 ARI 28

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 Cardinals

Their offense played far below its usual level. In a fresh game against the 49ers they would win 58% of the time; with this day’s form, 5%.

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

UnitThis gameUsual levelBetter or worse than usual
49ers offenseEPA per play gained +0.23 +0.14 better by 0.09
49ers defenseEPA per play allowed −0.03 +0.06 better by 0.09
Cardinals offenseEPA per play gained −0.03 +0.14 worse by 0.17
Cardinals defenseEPA per play allowed +0.23 +0.13 worse by 0.10

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

49ers win 95% of them, Cardinals 5%, counting the 1% still level after regulation as half each. The line is what actually happened: 49ers by 8.

Show as a table
Final margin in the replaysShare of replays
49ers by 17+67.5%
49ers by 9–1617.8%
49ers by 1–89.3%
Level after regulation0.8%
Cardinals by 1–83.4%
Cardinals by 9–161.1%
Cardinals by 17+0.2%

Where the luck was

Take the luck out

The final margin was 49ers by 8. Remove the luck, one kind at a time, and it becomes 49ers by 24.9.

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.

  • M. Nugent, 27 yds made · 97% expected
  • M. Nugent, 43 yds made · 84% expected
  • R. Gould, 41 yds missed · 87% expected
  • R. Gould, 37 yds missed · 91% expected
  • Extra point missed · 93% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

Cardinals’ chance of winning

As low as 0% and as high as 67%. 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 Cardinals were ahead in it, below while the 49ers were.
#WhenWhat happenedWin probability forNext drive
1 Q1 14:19 The Cardinals converted 3rd & 43rd & 4th downs · 42% expected +10% ARI ARI: Field goal
2 Q2 2:00 The Cardinals converted 4th & 33rd & 4th downs · 48% expected +11% ARI ARI: Field goal
3 Q2 0:45 The Cardinals were stopped on 3rd & 83rd & 4th downs · 29% expectedFalse Start on the Cardinals (Dan Arnold), 5 yardsPre-snap flags · 7 flags in 587 snaps before, position avg 1 per 276 +10% SF ARI: Field goal
4 Q2 0:14 The 49ers fumbled and the Cardinals recoveredFumble bounces · loose balls are close to 50/50 +11% ARI SF: Missed field goal
5 Q3 11:12 R. Gould missed 41-yard field goalKicks · 87% expected for him +14% ARI SF: Touchdown
6 Q3 2:35 The Cardinals converted 4th & 53rd & 4th downs · 37% expected +10% ARI ARI: Touchdown
7 Q4 9:04 The Cardinals were stopped on 4th & 23rd & 4th downs · 57% expected +13% SF ARI: Turnover
8 Q4 5:51 The Cardinals converted 4th & 13rd & 4th downs · 70% expected +14% ARI ARI: Turnover

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.

  • Dre Kirkpatrick (ARI CB), out · 0.6 pts
  • Corey Peters (ARI DL), out (IR) · 0.4 pts
  • Jalen Thompson (ARI S), out · 0.4 pts
  • Zane Gonzalez (ARI K), out (IR) · 0.3 pts
  • Maxx Williams (ARI TE), out · 0.2 pts
  • Nick Mullens (SF QB), out (IR), replaced by c.beathard · 2.0 pts
  • Richard Sherman (SF CB), out · 1.6 pts
  • Deebo Samuel (SF WR), out · 1.0 pts
  • Jimmie Ward (SF DB), out · 0.5 pts
  • Javon Kinlaw (SF DT), out · 0.3 pts
  • Kevin Givens (SF DL), out · 0.3 pts
  • Tom Compton (SF OL), 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

49ers 100% · Cardinals 0%

Final margin
49ers by 8
Luck in points
16.9 for the Cardinals
Luck-adjusted margin
49ers by 24.9
Replay with same day's form
49ers 95% · Cardinals 5% 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 16 2020 games · 49ers · Cardinals

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