luckadjusted

Week 17 2024 · December 28, 2024

Cardinals at Rams, Week 17 2024: who deserved to win?

The Rams stole one. They beat the Cardinals 13–9, but replayed with the way both teams actually played, the Cardinals win 8 of 10. Luck ran their way: judgment calls alone were worth 3.2 points to the Rams.

The Rams won on an off day: their offense played far below its usual level. In a fresh game against the Cardinals they would win 67% of the time; with this day’s form, 17%. The numbers

Before kickoff the Rams were 68% favorites. The biggest swing (Q4, 0:42 left): the Cardinals were intercepted on a well-placed throw, worth 35 points of win probability to the Rams.

Final

Arizona Cardinals 9
Los Angeles Rams 13

December 28, 2024 · SoFi Stadium · Closing line: Rams −6.5

Luck index +83 Rams very lucky · −83 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. Cardinals win 8, Rams win 2.

  1. 1 ARI 45 LA 14
  2. 2 ARI 34 LA 13
  3. 3 ARI 30 LA 14
  4. 4 ARI 31 LA 19
  5. 5 ARI 37 LA 27
  6. 6 ARI 17 LA 10
  7. 7 ARI 27 LA 23
  8. 8 ARI 22 LA 20
  9. 9 ARI 13 LA 16
  10. 10 ARI 16 LA 27

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.

The Rams won on an off day

Their offense played far below its usual level. In a fresh game against the Cardinals they would win 67% of the time; with this day’s form, 17%.

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

UnitThis gameUsual levelBetter or worse than usual
Cardinals offenseEPA per play gained +0.08 +0.09 worse by 0.01
Cardinals defenseEPA per play allowed −0.03 +0.13 better by 0.16
Rams offenseEPA per play gained −0.03 +0.10 worse by 0.13
Rams defenseEPA per play allowed +0.08 +0.09 better by 0.01

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

Cardinals win 83% of them, Rams 17%, counting the 2% still level after regulation as half each. The line is what actually happened: Rams by 4.

Show as a table
Final margin in the replaysShare of replays
Cardinals by 17+30.8%
Cardinals by 9–1621.9%
Cardinals by 1–828.2%
Level after regulation2.0%
Rams by 1–810.7%
Rams by 9–164.6%
Rams by 17+1.7%

Where the luck was

Take the luck out

The final margin was Rams by 4. Remove the luck, one kind at a time, and it becomes Cardinals by 3.4.

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. Karty, 53 yds made · 70% expected
  • C. Ryland, 28 yds made · 96% expected
  • J. Karty, 25 yds made · 98% expected
  • Extra point missed · 95% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

When it happened

Rams’ 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 Rams were ahead in it, below while the Cardinals were.
#WhenWhat happenedWin probability forNext drive
1 Q2 11:10 The Cardinals were stopped on 4th & 13rd & 4th downs · 74% expected +10% LA ARI: Punt
2 Q2 8:35 Ineligible Downfield Pass on the Cardinals, 5 yards, wiping out the playJudgment calls +12% LA LA: Touchdown
3 Q4 14:04 C. Ryland made 28-yard field goalKicks · 96% expected for him +13% LA ARI: Turnover
4 Q4 10:41 Offensive Holding on the Rams, 10 yards, wiping out the playJudgment calls +8% ARI ARI: Turnover
5 Q4 10:08 Defensive Offside on the Cardinals (Roy Lopez), 5 yards, wiping out the playPre-snap flags · 2 flags in 2195 snaps before, position avg 1 per 528 +24% LA LA: Field goal
6 Q4 6:36 J. Karty made 25-yard field goalKicks · 98% expected for him +10% ARI LA: Punt
7 Q4 1:35 The Cardinals converted 3rd & 43rd & 4th downs · 46% expected +10% ARI ARI: Turnover
8 Q4 0:42 The Cardinals were intercepted on a well-placed throwInterceptions · 0% expected to stay out of the defense's hands +35% LA –

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.

  • Rob Havenstein (LA T), out · 1.0 pts
  • Jonah Williams (ARI T), out (IR) · 1.0 pts
  • Blake Gillikin (ARI P), out (IR) · 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

Cardinals 67% · Rams 33%

Final margin
Rams by 4
Luck in points
7.4 for the Rams
Luck-adjusted margin
Cardinals by 3.4
Replay with same day's form
Cardinals 83% · Rams 17% 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; injuries from snap counts and injury reports.

Methodology and validation · All Week 17 2024 games · Cardinals · Rams

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