luckadjusted
NFL Week 9 · 2026

Week 15 2021 · December 19, 2021

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

Cardinals at Lions, Week 15 2021: who deserved to win?

The Lions beat the Cardinals 30–12, a result the replays rarely give: with the way both teams actually played, the Cardinals win 8 of 10. Luck ran their way: 3rd & 4th downs alone were worth 8 points of win probability to the Lions.

Before kickoff the Cardinals were 83% favorites.

Final

Arizona Cardinals 12
Detroit Lions 30

December 19, 2021 · Ford Field · Closing line: Cardinals −13

Luck index +82 Lions very lucky · −82 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, Lions win 2.

  1. 1 ARI 31 DET 3
  2. 2 ARI 30 DET 10
  3. 3 ARI 24 DET 7
  4. 4 ARI 26 DET 13
  5. 5 ARI 27 DET 17
  6. 6 ARI 16 DET 10
  7. 7 ARI 17 DET 13
  8. 8 ARI 30 DET 28
  9. 9 ARI 10 DET 13
  10. 10 ARI 3 DET 16

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

Cardinals win 82% of them, Lions 18%, counting the 2% still level after regulation as half each. The line is what actually happened: Lions by 18.

Show as a table
Final margin in the replaysShare of replays
Cardinals by 17+33.3%
Cardinals by 9–1622.9%
Cardinals by 1–825.1%
Level after regulation1.7%
Lions by 1–810.3%
Lions by 9–165.0%
Lions by 17+1.7%

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 +1.2 points to the Lions: the final margin was Lions by 18, without the luck Lions by 16.8. 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.

  • R. Patterson, 37 yds made · 93% expected
  • M. Prater, 29 yds made · 96% expected
  • M. Prater, 29 yds made · 96% expected
  • R. Patterson, 47 yds made · 80% expected
  • R. Patterson, 45 yds made · 84% expected
Bar: expected chance of a make. Filled dot: made. Open dot: missed or blocked.

Penalties: Cardinals 7 for 83 yards, Lions 6 for 49 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 half toward luck; pre-snap fouls, which repeat, don’t count. How calls are valued

WhenFlagWin probability for
Q1 6:14 Delay of Game on the Lions, 5 yards · pre-snap +2% ARI +0.4 pts
Q1 6:10 Illegal Formation on the Lions, 5 yards · pre-snap +1% ARI +0.5 pts
Q1 4:58 False Start on the Cardinals, 5 yards · pre-snap +3% DET +0.8 pts
Q2 11:23 False Start on the Lions, 5 yards · pre-snap +1% ARI +0.6 pts
Q2 11:10 False Start on the Cardinals, 5 yards · pre-snap +2% DET +0.7 pts
Q2 7:40 False Start on the Lions, 5 yards · pre-snap +1% ARI +0.7 pts
Q2 1:53 Roughing the Passer on the Cardinals (Chandler Jones), 15 yards +5% DET +1.4 pts
Q2 1:16 Roughing the Passer on the Cardinals (Jordan Phillips), 15 yards +2% DET +1.3 pts
Q2 0:19 Unnecessary Roughness on the Cardinals (Jordan Phillips), 15 yards +2% DET +1.0 pts
Q3 1:09 Roughing the Passer on the Cardinals (Zach Allen), 15 yards 0% DET +1.5 pts
Q4 14:29 Offensive Holding on the Lions, 10 yards 0% ARI +1.3 pts
Q4 13:00 Defensive Pass Interference on the Lions (Will Harris), 19 yards 0% ARI +2.3 pts
Q4 4:30 Defensive Pass Interference on the Cardinals (Marco Wilson), 13 yards 0% DET +1.9 pts

Cardinals penalties, every game · Lions penalties, every game · All teams, 2021

When it happened

Lions’ chance of winning

As low as 50% 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 Lions were ahead in it, below while the Cardinals were.
#WhenWhat happenedWin probability forNext drive
1 Q1 13:27 The Lions converted 3rd & 43rd & 4th downs · 44% expected +3% DET DET: Field goal
2 Q1 11:26 The Lions converted 3rd & 53rd & 4th downs · 39% expected +4% DET DET: Field goal
3 Q1 2:55 The Lions converted 3rd & 53rd & 4th downs · 39% expected +5% DET DET: Touchdown
4 Q1 0:50 The Lions converted 3rd & 53rd & 4th downs · 39% expected +6% DET DET: Touchdown
5 Q2 2:02 The Cardinals were stopped on 4th & 33rd & 4th downs · 46% expected +6% DET ARI: End of half
6 Q2 1:53 Roughing the Passer on the Cardinals (Chandler Jones), 15 yardsJudgment calls · 8 flags in 1988 snaps before, position avg 1 per 409 +5% DET DET: Touchdown
7 Q2 0:31 The Lions converted 4th & 13rd & 4th downs · 72% expected +4% DET DET: Touchdown
8 Q3 8:59 The Lions fumbled and the Cardinals recoveredFumble bounces · loose balls are close to 50/50 +3% ARI DET: 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.

  • T.J. Hockenson (DET TE), out (IR) · 1.0 pts
  • Jerry Jacobs (DET CB), out (IR) · 0.6 pts
  • Trinity Benson (DET WR), out · 0.5 pts
  • D'Andre Swift (DET RB), out · 0.4 pts
  • Jonah Jackson (DET G), out · 0.4 pts
  • Tracy Walker (DET FS), out · 0.3 pts
  • Trey Flowers (DET LB), out (IR) · 0.3 pts
  • Austin Seibert (DET K), out (IR) · 0.2 pts
  • Julian Okwara (DET LB), out · 0.1 pts
  • J.J. Watt (ARI DE), out (IR) · 1.1 pts
  • DeAndre Hopkins (ARI WR), out (IR) · 1.1 pts
  • Rodney Hudson (ARI C), out (IR) · 0.6 pts
  • Robert Alford (ARI CB), out (IR) · 0.4 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 0% · Lions 100%

Final margin
Lions by 18
Luck in points
1.2 for the Lions
Luck-adjusted margin
Lions by 16.8
Replay with same day's form
Cardinals 82% · Lions 18% unchanged: why
How much of each is luck?

0% treats it as skill, 100% as pure luck. The tick is our fit.

What counts

None by default: our tests measured no carryover after a lucky break. Slide it up to count a break for more than its own swing. 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 · Cardinals · Lions

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