Week 5 2021 · October 10, 2021
No FTN charting for this game (drops and interception-worthy throws are not modelled).
49ers at Cardinals, Week 5 2021: who deserved to win?
The Cardinals beat the 49ers 17–10, but the 49ers played well enough to win it: they take 7 of 10 replays with the same day's form. Luck ran their way: injuries alone were worth 7.9 points to the Cardinals.
The Cardinals won on an off day: their offense played far below its usual level. In a fresh game against the 49ers they would win 68% of the time; with this day’s form, 28%. The numbers
Before kickoff the Cardinals were 67% favorites. The biggest swing (Q4, 9:23 left): the 49ers were stopped on 4th & 1, worth 14 points of win probability to the Cardinals.
Final
 San Francisco 49ers | 10 |
|---|---|
 Arizona Cardinals | 17 |
Replay with same day's form
Luck index +72 Cardinals very lucky · −72 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. 49ers win 7, Cardinals win 3.
- 1 SF 41 ARI 17
- 2 SF 31 ARI 13
- 3 SF 20 ARI 6
- 4 SF 27 ARI 17
- 5 SF 20 ARI 13
- 6 SF 20 ARI 16
- 7 SF 23 ARI 21
- 8 SF 21 ARI 23
- 9 SF 16 ARI 23
- 10 SF 7 ARI 22
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.
The Cardinals won on an off day
Their offense played far below its usual level. In a fresh game against the 49ers they would win 68% of the time; with this day’s form, 28%.
Same teams, fresh game
Replay with same day's form
39 points apart for the Cardinals: 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 |
|---|---|---|---|
| 49ers offenseEPA per play gained | −0.10 | +0.15 | worse by 0.24 |
| 49ers defenseEPA per play allowed | +0.07 | +0.06 | worse by 0.01 |
| Cardinals offenseEPA per play gained | +0.07 | +0.18 | worse by 0.11 |
| Cardinals defenseEPA per play allowed | −0.10 | +0.11 | better by 0.21 |
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 72% of them, Cardinals 28%, counting the 3% still level after regulation as half each. The line is what actually happened: Cardinals by 7.
Show as a table
| Final margin in the replays | Share of replays |
|---|---|
| 49ers by 17+ | 22.0% |
| 49ers by 9–16 | 23.1% |
| 49ers by 1–8 | 25.0% |
| Level after regulation | 3.4% |
| Cardinals by 1–8 | 15.8% |
| Cardinals by 9–16 | 7.2% |
| Cardinals by 17+ | 3.5% |
Where the luck was
Take the luck out
The final margin was Cardinals by 7. Remove the luck, one kind at a time, and it becomes 49ers by 6.6.
The kicks
How likely each kicker was to make that kick (his own record, the distance and the weather), and what happened.
- M. Prater, 21 yds made · 99% expected
- M. Prater, 61 yds missed · 56% expected
- J. Slye, 47 yds made · 78% expected
When it happened
Cardinals’ chance of winning
Numbers mark the biggest luck moments, listed below.
| # | When | What happened | Win probability for | Next drive |
|---|---|---|---|---|
| 1 | Q2 11:34 | The 49ers were stopped on 4th & 13rd & 4th downs · 65% expected | +6% ARI | SF: Punt |
| 2 | Q3 12:54 | The 49ers converted 3rd & 93rd & 4th downs · 28% expected | +6% SF | SF: Punt |
| 3 | Q3 9:12 | The 49ers converted 4th & 53rd & 4th downs · 39% expected | +6% SF | SF: Punt |
| 4 | Q4 12:10 | Offensive Holding on the 49ers (Ross Dwelley), 10 yardsJudgment calls · 7 flags in 1344 snaps before, position avg 1 per 269 | +8% ARI | ARI: Turnover |
| 5 | Q4 9:23 | The 49ers were stopped on 4th & 13rd & 4th downs · 72% expected | +14% ARI | SF: Turnover on downs |
| 6 | Q4 8:45 | The Cardinals fumbled and the 49ers recoveredFumble bounces · loose balls are close to 50/50 | +8% SF | ARI: Touchdown |
| 7 | Q4 7:56 | The 49ers were stopped on 3rd & 43rd & 4th downs · 44% expected | +6% ARI | SF: Turnover on downs |
| 8 | Q4 7:53 | The 49ers were stopped on 4th & 43rd & 4th downs · 44% expected | +14% ARI | SF: Field goal |
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.
- Byron Murphy (ARI CB), out · 0.9 pts
- Marco Wilson (ARI CB), out · 0.5 pts
- Justin Murray (ARI OL), out (IR) · 0.4 pts
- Jimmy Garoppolo (SF QB), out, replaced by t.lance · 6.3 pts
- George Kittle (SF TE), out (IR) · 1.1 pts
- K'Waun Williams (SF CB), out · 0.4 pts
- Jason Verrett (SF CB), out (IR) · 0.4 pts
- Dre Greenlaw (SF LB), out (IR) · 0.3 pts
- Robbie Gould (SF K), out (IR) · 0.3 pts
- Richie James (SF WR), out (IR) · 0.3 pts
- Tarvarius Moore (SF DB), out (IR) · 0.3 pts
- Justin Skule (SF OL), 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
49ers 42% · Cardinals 58%
- Final margin
- Cardinals by 7
- Luck in points
- 13.5 for the Cardinals
- Luck-adjusted margin
- 49ers by 6.5
- Replay with same day's form
- 49ers 72% · Cardinals 28% 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 5 2021 games · 
49ers · 
Cardinals
More from Week 5 2021
- Rams at Seahawks LA 26–17 · replay 73% for the winner
- Jets vs Falcons ATL 27–20 · replay 76% for the winner
- Broncos at Steelers PIT 27–19 · replay 52% for the winner
- Lions at Vikings MIN 19–17 · replay 51% for the winner
- Packers at Bengals GB 25–22 · replay 86% for the winner
- Dolphins at Buccaneers TB 45–17 · replay 99% for the winner
- Patriots at Texans NE 25–22 · replay 76% for the winner
- Saints at Washington NO 33–22 · replay 34% for the winner
- Eagles at Panthers PHI 21–18 · replay 38% for the winner
- Titans at Jaguars TEN 37–19 · replay 62% for the winner
- Bears at Raiders CHI 20–9 · replay 52% for the winner
- Browns at Chargers LAC 47–42 · replay 53% for the winner
- Giants at Cowboys DAL 44–20 · replay 71% for the winner
- Bills at Chiefs BUF 38–20 · replay 43% for the winner
- Colts at Ravens BAL 31–25 · replay 69% for the winner