Divisional round 2023 · January 21, 2024
Chiefs at Bills, Divisional round 2023: who deserved to win?
The Chiefs beat the Bills 27–24, and the replays lean their way: with the same day's form, they win 8 of 10. The Bills had the bounces: 3rd & 4th downs alone were worth 8 points of win probability to the Bills.
An off day for the Bills: their defense played far below its usual level. In a fresh game against the Chiefs they would win 56% of the time; with this day’s form, 21%. The numbers
Before kickoff the Bills were 57% favorites. The biggest swing (Q4, 1:47 left): T. Bass missed a 44-yard field goal, worth 30 points of win probability to the Chiefs.
Final
 Kansas City Chiefs | 27 |
|---|---|
 Buffalo Bills | 24 |
Replay with same day's form
Luck index +21 Chiefs about even · −21 Bills
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. Chiefs win 8, Bills win 2.
- 1 KC 37 BUF 9
- 2 KC 29 BUF 10
- 3 KC 23 BUF 7
- 4 KC 34 BUF 21
- 5 KC 17 BUF 7
- 6 KC 31 BUF 24
- 7 KC 17 BUF 13
- 8 KC 16 BUF 15
- 9 KC 17 BUF 20
- 10 KC 17 BUF 28
Your call
Did the Chiefs 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 Bills
Their defense played far below its usual level. In a fresh game against the Chiefs they would win 56% of the time; with this day’s form, 21%.
Same teams, fresh game
Replay with same day's form
35 points apart for the Bills: 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 |
|---|---|---|---|
| Chiefs offenseEPA per play gained | +0.41 | +0.17 | better by 0.24 |
| Chiefs defenseEPA per play allowed | +0.14 | +0.04 | worse by 0.11 |
| Bills offenseEPA per play gained | +0.14 | +0.20 | worse by 0.05 |
| Bills defenseEPA per play allowed | +0.41 | +0.08 | worse by 0.33 |
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
Chiefs win 79% of them, Bills 21%, counting the 2% still level after regulation as half each. The line is what actually happened: Chiefs by 3.
Show as a table
| Final margin in the replays | Share of replays |
|---|---|
| Chiefs by 17+ | 27.2% |
| Chiefs by 9–16 | 21.5% |
| Chiefs by 1–8 | 28.9% |
| Level after regulation | 2.4% |
| Bills by 1–8 | 12.2% |
| Bills by 9–16 | 5.8% |
| Bills by 17+ | 2.1% |
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.
- T. Bass, 27 yds made · 96% expected
- H. Butker, 47 yds made · 75% expected
- H. Butker, 29 yds made · 97% expected
- T. Bass, 44 yds missed · 77% expected
Penalties: Chiefs 2 for 15 yards, Bills 5 for 28 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 14:52 | Illegal Bat on the Bills (Dalton Kincaid), 10 yards | +2% KC +0.8 pts |
| Q2 11:45 | Defensive Holding on the Bills (Rasul Douglas), 5 yards | 0% KC +0.3 pts |
| Q2 0:20 | Offensive Holding on the Chiefs, 10 yards | 0% BUF +0.1 pts |
| Q3 7:54 | Illegal Use of Hands on the Chiefs (Trent McDuffie), 5 yards | +4% BUF +0.9 pts |
| Q3 3:29 | Delay of Game on the Bills, 5 yards · pre-snap | +4% KC +0.6 pts |
| Q4 14:20 | Encroachment on the Bills (Tim Settle), 5 yards · pre-snap | 0% KC 0.0 pts |
| Q4 9:31 | Defensive Pass Interference on the Bills (Dorian Williams), 3 yards | +6% KC +1.0 pts |
Chiefs penalties, every game · Bills penalties, every game · All teams, 2023
When it happened
Bills’ chance of winning
As low as 0% and as high as 70%. Numbers mark the biggest luck moments, listed below.
| # | When | What happened | Win probability for | Next drive |
|---|---|---|---|---|
| 1 | Q1 11:46 | The Bills converted 3rd & 43rd & 4th downs · 51% expected | +7% BUF | BUF: Field goal |
| 2 | Q3 3:29 | The Bills converted 3rd & 133rd & 4th downs · 28% expectedDelay of Game on the Bills, 5 yardsPre-snap flags | +8% BUF | BUF: Touchdown |
| 3 | Q4 12:57 | The Bills were stopped on 4th & 53rd & 4th downs · 47% expected | +8% KC | BUF: Punt |
| 4 | Q4 5:47 | The Bills got away with an interception-worthy throwInterceptions · defenses catch 50% of interception-worthy throws | +15% BUF | BUF: Missed field goal |
| 5 | Q4 4:52 | The Bills converted 4th & 33rd & 4th downs · 58% expected | +16% BUF | BUF: Missed field goal |
| 6 | Q4 3:20 | The Bills converted 3rd & 43rd & 4th downs · 51% expected | +9% BUF | BUF: Missed field goal |
| 7 | Q4 1:55 | The Bills were stopped on 3rd & 93rd & 4th downs · 34% expected | +10% KC | BUF: Missed field goal |
| 8 | Q4 1:47 | T. Bass missed a 44-yard field goalKicks · 77% expected for him | +30% KC | – |
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.
- Christian Benford (BUF CB), out · 0.8 pts
- Terrel Bernard (BUF LB), out · 0.4 pts
- Wanya Morris (KC T), out · 0.5 pts
- Bryan Cook (KC FS), out (IR) · 0.3 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
Chiefs 35% · Bills 65%
- Final margin
- Chiefs by 3
- Luck in points
- 5.8 for the Chiefs
- Luck-adjusted margin
- Bills by 2.8
- Replay with same day's form
- Chiefs 79% · Bills 21% 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; injuries from snap counts and injury reports.
Methodology and validation · All Divisional round 2023 games · 
Chiefs · 
Bills
More from Divisional round 2023
- Texans at Ravens BAL 34–10 · replay 87% for the winner
- Packers at 49ers SF 24–21 · replay 69% for the winner
- Buccaneers at Lions DET 31–23 · replay 73% for the winner