Game Predictions Week 9

Game probabilities for week 9 NFL games are listed below. The probabilities are based on an efficiency win model explained here and here. The model considers offensive and defensive efficiency stats including running, passing, sacks, turnover rates, and penalty rates. Team stats are adjusted for previous opponent strength. Games in which the model disagrees with consensus favorites are highlighted in red.

Vprob	Visitor	Home	Hprob
0.11	ARI	TB	0.89
0.20	CAR	TEN	0.80
0.51	CIN	BUF	0.49
0.56	DEN	DET	0.44
0.52	GB	KC	0.48
0.69	JAX	NO	0.31
0.65	SD	MIN	0.35
0.23	SF	ATL	0.77
0.71	WAS	NYJ	0.29
0.69	SEA	CLE	0.31
0.54	HOU	OAK	0.46
0.43	NE	IND	0.57
0.65	DAL	PHI	0.35
0.16	BAL	PIT	0.84

Week 8 Efficiency Rankings

NFL team efficiency rankings are listed below in terms of generic winning probability. The GWP is the probability a team would beat the league average team at a neutral site. Each team's opponent's average GWP is also listed, which can be considered to-date strength of schedule. GWP modifies the generic win probability to reflect the strength of past opponents. OGWP is each team's offensive GWP, i.e. it's the team's GWP assuming it had a league-average defense. DGWP is vice-versa. Rankings are based on a logistic regression model applied to data through week 8. A full explanation of the methodology can be found here.

Rank	Team	Last Wk	GWP	Opp GWP	OGWP	DGWP
1	NE	2	0.91	0.46	0.81	0.70
2	IND	1	0.90	0.50	0.76	0.72
3	DAL	4	0.77	0.41	0.69	0.61
4	TB	3	0.76	0.49	0.67	0.60
5	PIT	5	0.71	0.42	0.60	0.61
6	SEA	9	0.65	0.42	0.56	0.55
7	JAX	8	0.61	0.55	0.60	0.54
8	SD	13	0.60	0.45	0.60	0.54
9	TEN	11	0.58	0.51	0.40	0.69
10	PHI	12	0.57	0.39	0.66	0.46
11	NYG	7	0.56	0.41	0.50	0.59
12	WAS	10	0.52	0.51	0.40	0.68
13	DEN	6	0.51	0.57	0.65	0.38
14	GB	15	0.50	0.47	0.54	0.50
15	CIN	14	0.48	0.52	0.64	0.44
16	BAL	24	0.40	0.31	0.38	0.55
17	HOU	18	0.39	0.50	0.46	0.40
18	KC	17	0.39	0.42	0.37	0.57
19	BUF	20	0.38	0.54	0.41	0.55
20	CLE	16	0.37	0.46	0.58	0.37
21	ARI	19	0.37	0.42	0.43	0.49
22	DET	22	0.36	0.41	0.40	0.50
23	MIN	21	0.36	0.44	0.46	0.45
24	CAR	23	0.34	0.46	0.46	0.42
25	NO	28	0.32	0.52	0.48	0.33
26	ATL	26	0.29	0.45	0.45	0.38
27	OAK	25	0.28	0.44	0.29	0.55
28	MIA	29	0.28	0.51	0.49	0.30
29	NYJ	27	0.24	0.49	0.43	0.31
30	CHI	30	0.19	0.49	0.30	0.40
31	STL	32	0.18	0.48	0.31	0.39
32	SF	31	0.14	0.46	0.22	0.42

This week the method of adjusting for opponent strength was improved. Instead of a single iteration of adjustment, the calculations now include as many iterations as required for full convergence. For example, a team that has usually dominated its opponents would have an apparently weaker opponent strength than is the case. Multiple iterations of opponent-strength adjustments corrects for this effect. CLE and BAL appear to be the only teams to be significantly affected.

Patriots or Colts Undefeated?

With the impending showdown between the NFL's top two teams, a lot of the discussion has mentioned the possibility of either the Patriots or Colts going undefeated. Not since the '72 Dolphins went 14-0 in the regular season has an NFL team repeated the feat. There are now 16 games in a regular season, making the achievement even more improbable.

Of course, only one of the two teams could go undefeated this year because they have to play each other. In this post, I'll examine which team is more likely to go 16-0--assuming each wins on Sunday.

The probability that either team would go undefeated is estimated based on a calculation of game-by-game win probabilities. Every permutation of outcomes of wins and losses is computed for each team. The combination that represents only wins and no losses is the probability that the team will be 16-0. The methodology is explained more fully in this post. In short, the probability estimate accounts for all major phases of team efficiency, to-date opponent strength, future opponent strength, and home field advantage in upcoming match-ups.

However, there is one important distinction between teams at this point. Still awaiting their bye, the Patriots and have played, and won, one more game than the Colts. This gives them a distinct advantage when comparing the two teams' chances of winning out. But it is still interesting to know just how possible it is for teams like the Patriots or Colts to do what hasn't been done for three and half decades.

And of course, it all depends on who wins on Sunday.

Both teams have been mercilessly efficient so far in 2007. Below are the efficiency stats for each team (unadjusted for opponent). Also listed is the NFL average (not including NE and IND) for each stat, so we can compare see just how good these two teams are.

Stat	IND	NE	NFL
O Pass	7.57	8.65	6.01
O Run	4.42	4.19	4.05
O Int Rate	0.013	0.011	0.032
O Fum Rate	0.013	0.015	0.027
D Pass	4.79	5.09	6.25
D Run	4.06	4.24	4.05
D Int Rate	0.039	0.042	0.031
Pen Rate	0.21	0.31	0.37

(Pass and run stats are yds per attempt. Fumble rate is fumbles per play. Int rate is in interceptions per attempt. Penalty rate is penalty yards per play.)

NE has the better passing game, but IND has the better running game and defends the pass better. NE gets more interceptions, but IND commits fewer penalties for fewer yards. All things considered, the two teams are about equal. NE has garnered more attention so far because of the fact they've scored more touchdowns, but they've played a considerably weaker schedule.

Below is a table of each team's to-date opponents and their generic win probability (GWP)--the probability a team will beat a notional league-average team at a neutral site. Opponent strengths do account for the beatings handed to them by IND and NE. In other words, NE's strength of schedule isn't penalized due to the pounding their opponents received at the hands of NE themselves. IND's opponents' have been slightly stronger than average with a 0.52 GWP, while NE's opponents' have been below average with a 0.45 GWP.

NE Opp	GWP	IND Opp	GWP
NYJ	0.23	NO	0.32
SD	0.62	TEN	0.58
BUF	0.43	HOU	0.34
CIN	0.50	DEN	0.66
CLE	0.38	TB	0.76
DAL	0.71	bye
MIA	0.23	JAX	0.64
WAS	0.50	CAR	0.33
Avg	0.45		0.52

Although both teams are about equal in (unadjusted) efficiency stats, after adjusting for opponent strength IND comes out on top with a 0.92 GWP compared to a 0.90 GWP for NE. Keep in mind these are estimations, so a difference of 0.02 is essentially a wash. We'll certainly find out more on Sunday.

Given about a 90% chance of winning a game against a league-average opponent at a neutral site, and assuming they win against the Colts, the Patriots would roughly have about a 0.90⁷ = 48% chance of going undefeated. If the Colts win Sunday, they would have about a 0.92⁸ = 51% chance of finishing undefeated.

But NFL games aren't against theoretical league-average opponents, and they aren't (normally) at neutral sites. NE has an slightly easier forthcoming schedule as their future opponents' GWP average is 0.43 while IND's future opponents average a slightly tougher 0.45 GWP.

NE Opp	GWP	IND Opp	GWP
bye		SD	0.62
BUF	0.43	KC	0.44
PHI	0.55	ATL	0.29
BAL	0.34	JAX	0.64
PIT	0.72	BAL	0.34
NYJ	0.23	OAK	0.31
MIA	0.23	HOU	0.34
NYG	0.53	TEN	0.58
Avg	0.43		0.45

NE's upcoming schedule and their associated outcome probabilities are listed below. The series probability that the a team would go undefeated is the product of the probabilities of winning each individual game. Keep in mind this assumes each team wins this Sunday.

Vprob	Visitor	Home	Hprob
0.90	NE	BUF	0.10
0.08	PHI	NE	0.92
0.93	NE	BAL	0.07
0.16	PIT	NE	0.84
0.02	NYJ	NE	0.98
0.02	MIA	NE	0.98
0.85	NE	NYG	0.15

Probability of New England going undefeated =
0.90 * 0.92 * 0.93 * 0.84 * 0.98 * 0.98 * 0.85 = 0.52

IND's upcoming schedule and their associated outcome probabilities are listed below.

Hprob	Visitor	Home	Vprob
0.83	IND	SD	0.17
0.05	KC	IND	0.95
0.95	IND	ATL	0.05
0.10	JAX	IND	0.90
0.94	IND	BAL	0.06
0.95	IND	OAK	0.05
0.03	HOU	IND	0.97
0.08	TEN	IND	0.92

Probability of Indianapolis going undefeated =
0.83 * 0.95 * 0.95 * 0.90 * 0.94 * 0.95 * 0.97 * 0.92 = 0.54

By the end of Sunday's game, one of the teams will see their chances swiftly go to zero.

Note: Republished with a correction to NE's probability.

QB Rating Week 7

The QB Wins Added Per 16 Games stat (+WP16) estimates how many wins a quarterback adds to his team's record over the course of a 16-game season. +WP16 is explained here and here. Last year's ratings can be found in the second link. Here is the list of 2007 QBs and their vital stats through week 7.

Rank	Name	Att	Yds	Air Yds	YAC	Int	Rush	Yds	Sk Yds	Fum	+WP16
1	Brady	229	2125	1248	877	2	8	11	44	3	3.94
2	Manning P	202	1578	1105	473	3	9	-7	31	1	3.78
3	Garrard	148	1141	680	461	0	30	134	73	2	2.58
4	Schaub	197	1581	1043	538	5	14	38	94	7	1.87
5	Palmer	224	1717	1129	588	9	7	11	75	1	1.79
6	Romo	239	1984	1162	822	9	14	81	83	3	1.74
7	Garcia	189	1504	724	780	0	19	40	45	3	1.72
8	Warner	112	883	576	307	3	5	0	30	5	1.64
9	Anderson	184	1496	943	553	8	15	30	63	3	1.48
10	Roethlisberger	166	1303	793	510	5	11	77	119	4	1.15
11	Hasselbeck	233	1705	935	770	6	12	14	80	1	0.83
12	Delhomme	86	624	313	311	1	6	26	46	1	0.81
13	Boller	117	662	402	260	2	7	22	30	1	0.67
14	Pennington	170	1211	757	454	7	15	18	83	0	0.57
15	Smith	84	461	303	158	1	8	67	74	2	0.42
16	Cutler	181	1406	768	638	8	16	74	40	5	0.40
17	McNabb	205	1447	737	710	2	17	56	116	4	0.36
18	Campbell	168	1181	619	562	5	20	93	42	5	0.27
19	Leinart	112	647	374	273	4	11	42	23	0	0.12
20	Manning E	227	1525	819	706	9	9	13	39	3	-0.21
21	McNair	157	922	455	467	2	9	26	37	4	-0.24
22	Young	114	703	414	289	6	32	129	22	3	-0.24
23	Harrington	213	1407	689	718	4	7	14	126	0	-0.25
24	Kitna	187	1480	823	657	6	16	42	152	8	-0.49
25	Favre	247	1715	755	960	6	12	6	73	3	-0.55
26	Huard	215	1470	768	702	7	9	-1	119	2	-0.62
27	Brees	247	1394	754	640	10	11	31	28	2	-0.73
28	Rivers	178	1312	683	629	7	11	2	77	5	-0.75
29	Green	141	987	515	472	7	7	32	53	2	-0.75
30	Griese	163	1203	573	630	6	5	8	77	4	-0.97
31	Lemon	107	643	335	308	4	7	25	51	1	-1.00
32	Culpepper	93	650	317	333	3	13	27	58	2	-1.00
33	Jackson	98	537	264	273	5	11	46	10	0	-1.23
34	Edwards	100	660	331	329	4	3	5	67	1	-1.39
35	Bulger	173	990	591	399	7	4	16	124	3	-1.46
36	Frerotte	85	499	298	201	8	2	3	21	1	-3.04
37	Grossman	89	500	284	216	6	4	9	82	1	-3.12
38	McCown J	68	494	247	247	5	9	46	55	7	-3.80
39	Dilfer	90	463	265	198	5	4	15	100	6	-4.27

I also thought it would be interesting to see how +WP16 compares to the official NFL Passer Rating. Kitna stands out as particularly overrated by the NFL Passer Rating. It appears to be mostly due to his 152 sack yards lost and 8 fumbles, both league-leading stats.

Name	Rank	+WP16	NFL PR Rank	NFL PR
Brady	1	3.94	1	137.9
Manning P	2	3.78	4	103.5
Garrard	3	2.58	5	102.9
Schaub	4	1.87	10	90.5
Palmer	5	1.79	11	89.1
Romo	6	1.74	7	95.6
Garcia	7	1.72	3	106.2
Warner	8	1.64	8	95.2
Anderson	9	1.48	12	88.9
Roethlisberger	10	1.15	6	101.1
Hasselbeck	11	0.83	13	88.7
Delhomme	12	0.81	2	111.8
Boller	13	0.67	26	78.4
Pennington	14	0.57	14	88.6
Smith	15	0.42	33	66.6
Cutler	16	0.40	18	84.2
McNabb	17	0.36	15	88.4
Campbell	18	0.27	25	78.5
Leinart	19	0.12	34	61.9
Manning E	20	-0.21	20	82.9
McNair	21	-0.24	23	80.2
Young	22	-0.24	31	68.0
Harrington	23	-0.25	22	80.9
Kitna	24	-0.49	9	93.9
Favre	25	-0.55	16	87.0
Huard	26	-0.62	24	79.8
Brees	27	-0.73	30	69.1
Rivers	28	-0.75	19	83.8
Green	29	-0.75	28	72.6
Griese	30	-0.97	17	86.0
Lemon	31	-1.00	32	66.8
Culpepper	32	-1.00	21	81.4
Jackson	33	-1.23	37	48.7
Edwards	34	-1.39	29	71.3
Bulger	35	-1.46	35	58.7
Frerotte	36	-3.04	39	44.2
Grossman	37	-3.12	38	45.2
McCown J	38	-3.80	27	75.2
Dilfer	39	-4.27	36	55.0

Season Win Projections Week 7

Season win totals and division standing projections are listed below. As before, projections are based on each team's opponent-adjusted generic win probability (GWP). The projections now account for future opponent strength. Total wins account for current and projected wins. Methodology can be found here.

Team	Rank	Proj GWP	Fut Opp	Current	Proj
AFC E
NE	2	0.86	0.55	7	14.7
BUF	20	0.40	0.51	2	6.0
NYJ	27	0.26	0.57	1	3.4
MIA	29	0.26	0.54	0	2.3
AFC N
PIT	5	0.73	0.47	4	11.3
CLE	16	0.54	0.42	3	8.4
CIN	14	0.61	0.43	2	8.1
BAL	24	0.24	0.63	4	6.1
AFC S
IND	1	0.89	0.52	6	14.9
JAX	8	0.61	0.52	4	10.1
TEN	11	0.57	0.52	4	9.7
HOU	18	0.38	0.55	4	7.4
AFC W
DEN	6	0.70	0.44	3	10.0
SD	13	0.53	0.53	3	8.3
KC	17	0.43	0.52	4	7.9
OAK	25	0.31	0.52	2	5.1
Team	Rank	Proj GWP	Fut Opp	Current	Proj
NFC E
DAL	4	0.70	0.54	6	12.3
NYG	7	0.64	0.51	5	10.8
WAS	10	0.54	0.58	4	9.4
PHI	12	0.51	0.57	2	7.1
NFC N
GB	15	0.56	0.43	5	10.6
DET	22	0.38	0.51	4	7.8
MIN	21	0.43	0.47	2	6.3
CHI	30	0.26	0.50	3	5.3
NFC S
TB	3	0.82	0.40	4	11.4
CAR	23	0.31	0.55	4	7.1
NO	28	0.36	0.42	2	5.6
ATL	26	0.32	0.51	1	3.8
NFC W
SS	9	0.74	0.38	4	10.6
ARI	19	0.50	0.41	3	7.5
SF	31	0.28	0.44	2	4.8
STL	32	0.26	0.44	0	2.6

Game Predictions Week 8

Game probabilities for week 8 NFL games are listed below. The probabilities are based on an efficiency win model explained here and here. The model considers offensive and defensive efficiency stats including running, passing, sacks, turnover rates, and penalty rates. Team stats are adjusted for previous opponent strength.

Vprob	Visitor	Home	Hprob
0.68	CLE	STL	0.32
0.57	DET	CHI	0.43
0.92	IND	CAR	0.08
0.82	NYG	MIA	0.18
0.20	OAK	TEN	0.80
0.58	PHI	MIN	0.42
0.57	PIT	CIN	0.43
0.51	BUF	NYJ	0.49
0.29	HOU	SD	0.71
0.27	JAX	TB	0.73
0.49	NO	SF	0.51
0.13	WAS	NE	0.87
0.27	GB	DEN	0.73

Edit: I was just reminded here that the NYG - MIA game is in London this week. I have revised the game probability to reflect this. The result was a swing of 0.06, so MIA's probability of winning went from 0.24 to 0.18. The Giants have benefited from another favorable scheduling aberration recently, when they hosted NO for one of their post-Katrina home games.

Also, if the SD-HOU game is played at an alternate site, the new probabilities would still have SD as the favorites at 0.64 to 0.36.

Week 7 Efficiency Rankings

Team efficiency rankings are listed below in terms of generic winning probability. The GWP is the probability a team would beat the league average team at a neutral site. Each team's opponent's average GWP is also listed, which can be considered to-date strength of schedule. GWP modifies the generic win probability to reflect the strength of past opponents. OGWP is each team's offensive GWP, i.e. it's the team's GWP assuming it had a league-average defense. DGWP is vice-versa. Rankings are based on a logistic regression model applied to data through week 7. A full explanation of the methodology can be found here.

Team	Rank	Last Wk	GWP	Opp GWP	OGWP	DGWP
IND	1	2	0.90	0.52	0.77	0.72
NE	2	1	0.88	0.44	0.79	0.70
TB	3	3	0.76	0.48	0.70	0.57
DAL	4	4	0.73	0.42	0.70	0.61
PIT	5	6	0.70	0.43	0.59	0.62
DEN	6	9	0.65	0.57	0.63	0.51
NYG	7	5	0.65	0.48	0.59	0.60
JAX	8	7	0.63	0.55	0.65	0.49
SEA	9	11	0.63	0.43	0.58	0.53
WAS	10	8	0.61	0.47	0.42	0.71
TEN	11	12	0.58	0.53	0.38	0.70
PHI	12	10	0.58	0.45	0.64	0.46
SD	13	14	0.56	0.51	0.60	0.47
CIN	14	13	0.55	0.56	0.63	0.45
GB	15	15	0.50	0.53	0.49	0.52
CLE	16	17	0.46	0.55	0.53	0.43
KC	17	18	0.45	0.44	0.37	0.58
HOU	18	16	0.42	0.52	0.49	0.44
ARI	19	23	0.41	0.50	0.47	0.49
BUF	20	19	0.41	0.64	0.41	0.52
MIN	21	21	0.40	0.45	0.43	0.46
DET	22	27	0.40	0.52	0.39	0.46
CAR	23	22	0.36	0.39	0.46	0.42
BAL	24	25	0.35	0.33	0.39	0.52
OAK	25	29	0.33	0.45	0.30	0.52
ATL	26	20	0.33	0.47	0.45	0.39
NYJ	27	24	0.32	0.54	0.47	0.33
NO	28	28	0.29	0.62	0.43	0.31
MIA	29	26	0.29	0.55	0.54	0.26
CHI	30	32	0.26	0.54	0.32	0.40
SF	31	30	0.23	0.54	0.24	0.49
STL	32	31	0.22	0.55	0.28	0.43

Behind the Prediction--TB at DET

Detroit is a 2 point favorite at home against Tampa Bay, but the efficiency model estimates that the Buccaneers have a 0.82 probability of upsetting the Lions. In this post I'll break down why the efficiency model favors the Bucs.

Detroit (3-2) is known these days for having a potent passing offense, while Tampa (4-2) is best known for its traditionally tough defense. But their efficiency stats tell a slightly different story.

Below is a table that lists each team's generic win probability (GWP) and their opponents' average GWP, each adjusted for to-date opponent strength. Also listed is each team's offensive and defensive GWP.

Team	GWP	O GWP	D GWP	Opp GWP	Opp O GWP	Opp D GWP
TB	0.82	0.66	0.61	0.49	0.50	0.49
DET	0.36	0.32	0.48	0.49	0.44	0.58

Tampa has been playing at a much higher level in terms of opponent-adjusted efficiency. The two teams have faced roughly equal opponents through week 6, with Tampa having faced average squads and Detroit facing stiffer defenses but weaker offenses.

The next table breaks down each team's (unadjusted) efficiency stats.

Team	O Pass	O Run	O Int Rate	O Fum	D Pass	D Run	D Int Rate	Pen Rate
TB	7.47	3.81	0.007	0.027	5.38	3.77	0.034	0.19
DET	6.06	3.75	0.042	0.060	6.66	3.91	0.049	0.34

The Buccaneers are better in every efficiency stat except defensive interception rate. The biggest advantage the Lions have on Sunday will be their home field. We also see that Tampa Bay is no longer a team reliant on its defense, but is a well-balanced team. Garcia has been very efficient and has thrown only one interception in six games. Tampa actually has the 4th most efficient passing game in the NFL. The Bucs appear to be a well disciplined team too, with one of the lowest penalty rates in the league.

A lot has been made of Martz's aggressive passing attack and the Lions' talent at wide receiver, but their offensive pass efficiency is slightly below average. Tampa Bay actually has a much better passing game so far in 2007.

Tampa has recently lost its starter at running back, but the rushing game has not been the strength of this team. Even if we dialed down their expected rushing efficiency, the Buccaneers would still be clear favorites.