Week 9 2021 · November 7, 2021
No FTN charting for this game (drops and interception-worthy throws are not modelled).
Cardinals at 49ers, Week 9 2021: who deserved to win?
The Cardinals beat the 49ers 31–17, and the replays back it up: with the way both teams actually played, the Cardinals win 8 of 10. The 49ers had the bounces: injuries alone were worth 14 points of win probability to the 49ers.
An off day for the 49ers: their offense and defense both played far below their usual level. In a fresh game against the Cardinals they would win 53% of the time; with this day’s form, 17%. The numbers
Before kickoff the 49ers were 66% favorites.
Final
 Arizona Cardinals | 31 |
|---|---|
 San Francisco 49ers | 17 |
Replay with same day's form
Luck index +17 Cardinals about even · −17 49ers
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, 49ers win 2.
- 1 ARI 39 SF 10
- 2 ARI 40 SF 17
- 3 ARI 40 SF 20
- 4 ARI 34 SF 18
- 5 ARI 26 SF 14
- 6 ARI 23 SF 14
- 7 ARI 27 SF 21
- 8 ARI 35 SF 33
- 9 ARI 26 SF 29
- 10 ARI 31 SF 45
Your call
Did the Cardinals earn it, or get lucky?
Three other ways to ask
Each answers a different question, so none of them replaces the replay above.
Before kickoff
The closing betting line, turned into a probability. What everyone knew before the game.
Same teams, fresh 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.
Only coin-flips re-rolled
Every kick, fumble bounce, drop, conversion and judgment call redrawn; everything else fixed. The narrowest view of luck.
An off day for the 49ers
Their offense and defense both played far below their usual level. In a fresh game against the Cardinals they would win 53% of the time; with this day’s form, 17%.
Same teams, fresh game
Replay with same day's form
36 points apart for the 49ers: the gap is how differently this game went from what the two teams usually are.
| Unit | This game | Usual level | Better or worse than usual |
|---|---|---|---|
| Cardinals offenseEPA per play gained | +0.48 | +0.18 | better by 0.31 |
| Cardinals defenseEPA per play allowed | −0.02 | +0.10 | better by 0.12 |
| 49ers offenseEPA per play gained | −0.02 | +0.14 | worse by 0.17 |
| 49ers defenseEPA per play allowed | +0.48 | +0.07 | worse by 0.41 |
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, 49ers 17%, counting the 2% still level after regulation as half each. The line is what actually happened: Cardinals by 14.
Show as a table
| Final margin in the replays | Share of replays |
|---|---|
| Cardinals by 17+ | 39.8% |
| Cardinals by 9–16 | 23.3% |
| Cardinals by 1–8 | 19.0% |
| Level after regulation | 2.1% |
| 49ers by 1–8 | 10.4% |
| 49ers by 9–16 | 3.7% |
| 49ers 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.
The kicks
How likely each kicker was to make that kick (his own record, the distance and the weather), and what happened.
- M. Prater, 26 yds made · 97% expected
- R. Gould, 26 yds made · 96% expected
Penalties: Cardinals 9 for 84 yards, 49ers 2 for 25 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
| When | Flag | Win probability for |
|---|---|---|
| Q1 6:08 | Delay of Game on the Cardinals, 5 yards · pre-snap | 0% SF 0.0 pts |
| Q1 4:05 | Offensive Holding on the Cardinals, 10 yards | +3% SF +1.4 pts |
| Q1 1:21 | Face Mask on the 49ers (Arik Armstead), 15 yards, wiping out the play | +7% ARI +2.8 pts |
| Q2 14:13 | Defensive Holding on the Cardinals (Byron Murphy), 5 yards | +2% SF +1.2 pts |
| Q2 6:47 | Taunting on the Cardinals, 14 yards | +3% SF +1.7 pts |
| Q2 2:36 | Defensive Pass Interference on the Cardinals (Marco Wilson), 16 yards | 0% SF +0.8 pts |
| Q3 7:40 | Roughing the Passer on the Cardinals (Leki Fotu), 15 yards | 0% SF +1.6 pts |
| Q3 4:56 | Illegal Double-Team Block on the Cardinals, 9 yards | 0% SF +0.8 pts |
| Q4 9:25 | Offensive Pass Interference on the 49ers (Mohamed Sanu), 10 yards | 0% ARI +1.1 pts |
| Q4 3:40 | False Start on the Cardinals, 5 yards · pre-snap | 0% SF +0.3 pts |
| Q4 3:40 | False Start on the Cardinals, 5 yards · pre-snap | 0% SF +0.1 pts |
Cardinals penalties, every game · 49ers penalties, every game · All teams, 2021
When it happened
49ers’ chance of winning
As low as 0% and as high as 58%. Numbers mark the biggest luck moments, listed below.
| # | When | What happened | Win probability for | Next drive |
|---|---|---|---|---|
| 1 | Q1 10:37 | The 49ers fumbled and the Cardinals recoveredFumble bounces · loose balls are close to 50/50 | +5% ARI | SF: Punt |
| 2 | Q1 4:05 | Offensive Holding on the Cardinals, 10 yardsJudgment calls | +3% SF | SF: Turnover |
| 3 | Q1 3:00 | The Cardinals converted 3rd & 183rd & 4th downs · 22% expected | +7% ARI | ARI: Touchdown |
| 4 | Q1 1:21 | Face Mask on the 49ers (Arik Armstead), 15 yards, wiping out the playJudgment calls · 6 flags in 2413 snaps before, position avg 1 per 266 | +7% ARI | ARI: Touchdown |
| 5 | Q2 12:34 | The 49ers fumbled and the Cardinals recoveredFumble bounces · loose balls are close to 50/50 | +3% ARI | SF: Touchdown |
| 6 | Q2 6:47 | Taunting on the Cardinals, 14 yardsJudgment calls | +3% SF | SF: Touchdown |
| 7 | Q2 6:18 | The Cardinals fumbled and recovered it themselvesFumble bounces · loose balls are close to 50/50 | +3% ARI | ARI: Field goal |
| 8 | Q3 5:03 | The 49ers converted 3rd & 113rd & 4th downs · 24% expected | +3% 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.
- Deommodore Lenoir (SF CB), out · 0.5 pts
- Jaquiski Tartt (SF SS), out (IR) · 0.4 pts
- Jimmie Ward (SF FS), out · 0.4 pts
- Jason Verrett (SF CB), out (IR) · 0.3 pts
- Javon Kinlaw (SF DT), out (IR) · 0.3 pts
- Kyler Murray (ARI QB), out, replaced by c.mccoy · 5.5 pts
- J.J. Watt (ARI DE), out (IR) · 1.3 pts
- DeAndre Hopkins (ARI WR), out · 1.2 pts
- A.J. Green (ARI WR), out (IR) · 1.1 pts
- Maxx Williams (ARI TE), 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 99% · 49ers 1%
- Final margin
- Cardinals by 14
- Luck in points
- 2.6 for the 49ers
- Luck-adjusted margin
- Cardinals by 16.6
- Replay with same day's form
- Cardinals 83% · 49ers 17% unchanged: why
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 9 2021 games · 
Cardinals · 
49ers
More from Week 9 2021
- Jets at Colts IND 45–30 · replay 81% for the winner
- Falcons at Saints ATL 27–25 · replay 62% for the winner
- Bills at Jaguars JAX 9–6 · replay 43% for the winner
- Browns at Bengals CLE 41–16 · replay 63% for the winner
- Broncos at Cowboys DEN 30–16 · replay 55% for the winner
- Texans at Dolphins MIA 17–9 · replay 59% for the winner
- Raiders at Giants NYG 23–16 · replay 14% for the winner
- Vikings at Ravens BAL 34–31 · replay 93% for the winner
- Patriots at Panthers NE 24–6 · replay 84% for the winner
- Chargers at Eagles LAC 27–24 · replay 78% for the winner
- Packers at Chiefs KC 13–7 · replay 67% for the winner
- Titans at Rams TEN 28–16 · replay 38% for the winner
- Bears at Steelers PIT 29–27 · replay 34% for the winner