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2008 QB numbers: Adjusted for strength of schedule

Posted by Chase Stuart on August 24, 2009

In the 2007 and 2008 off-seasons I wrote articles adjusting QB statistics for strength of schedule. Today brings the summer '09 update. As always, I've done essentially the same analysis for our fantasy football fans over at Footballguys.com.

Let's start with a look at the 2008 leaders in adjusted yards per attempt, defined as (passing yards + PTD*20 - INT*45)/attempts. All QBs with a minimum of 100 attempts are listed; the league average was 6.45 AY/A.

name			att	pyd	ptd	int	ay/a
Philip Rivers		478	4009	34	11	8.77
Drew Brees		635	5069	34	17	7.85
Chad Pennington		476	3653	19	 7	7.81
Tarvaris Jackson	149	1056	 9	 2	7.69
Matt Schaub		380	3043	15	10	7.61
Kurt Warner		599	4582	30	14	7.60
Matt Ryan		434	3440	16	11	7.52
Aaron Rodgers		536	4038	28	13	7.49
Tony Romo		450	3448	26	14	7.42
Jake Delhomme		414	3288	15	12	7.36
Peyton Manning		555	4002	27	12	7.21
Jeff Garcia		376	2712	12	 6	7.13
Matt Cassel		516	3693	21	11	7.01
Jay Cutler		616	4526	25	18	6.84
Donovan McNabb		571	3916	23	11	6.80
Shaun Hill		288	2046	13	 8	6.76
Eli Manning		479	3238	21	10	6.70
Seneca Wallace		242	1532	11	 3	6.68
Trent Edwards		374	2699	11	10	6.60
Jason Campbell		506	3245	13	 6	6.39
Ben Roethlisberger	468	3308	17	15	6.35
Joe Flacco		428	2971	14	12	6.33
Sage Rosenfels		174	1431	 6	10	6.33
JaMarcus Russell	368	2423	13	 8	6.31
Kerry Collins		415	2676	12	 7	6.27
David Garrard		535	3620	15	13	6.23
J.T. O'Sullivan		220	1678	 8	11	6.10
Kyle Orton		465	2972	18	12	6.00
Tyler Thigpen		420	2608	18	12	5.78
Gus Frerotte		301	2157	12	15	5.72
Brett Favre		522	3472	22	22	5.60
Dan Orlovsky		255	1616	 8	 8	5.55
Marc Bulger		440	2720	11	13	5.35
Jon Kitna		120	 758	 5	 5	5.28
Daunte Culpepper	115	 786	 4	 6	5.18
Derek Anderson		283	1615	 9	 8	5.07
Carson Palmer		129	 731	 3	 4	4.74
Brian Griese		184	1073	 5	 7	4.66
Ryan Fitzpatrick	372	1905	 8	 9	4.46
Matt Hasselbeck		209	1216	 5	10	4.14
J.P. Losman		104	 584	 2	 5	3.84


Now we need to adjust those numbers for strength of schedule; the full explanation of the process used to do so can be found here. What we do is adjust each QB and each defense for strength of schedule, to get a true rating for each QB and defense. Let’s start with the defenses first. I've put the defenses that faced the toughest schedules in bold (and therefore should be considered better than their raw numbers); the defenses that faced the easiest schedules (read: worst QBs) are in italics (indicating that they are worse than their raw numbers):

Team                    Adj     Raw      SOS
Pittsburgh Steelers	3.99	4.13	 0.14
Baltimore Ravens	4.40	4.36	-0.04
Tampa Bay Buccaneers	5.17	5.50	 0.33
Tennessee Titans	5.40	4.87	-0.53
Indianapolis Colts	5.43	5.53	 0.10
Philadelphia Eagles	5.51	5.46	-0.05
Green Bay Packers	5.51	5.58	 0.07
Chicago Bears		5.65	5.65	 0.00
Washington Redskins	5.73	5.79	 0.06
Carolina Panthers	5.87	6.21	 0.34
Oakland Raiders		6.10	6.57	 0.47
New York Giants		6.13	5.95	-0.18
Cleveland Browns	6.13	6.22	 0.08
New Orleans Saints	6.27	6.54	 0.27
Minnesota Vikings	6.29	6.63	 0.34
San Diego Chargers	6.33	6.44	 0.12
Miami Dolphins		6.39	6.18	-0.20
Cincinnati Bengals	6.45	6.50	 0.05
Kansas City Chiefs	6.50	6.97	 0.46
Atlanta Falcons		6.56	6.78	 0.22
San Francisco 49ers	6.83	6.55	-0.28
Dallas Cowboys		6.84	6.71	-0.13
New York Jets		6.84	6.72	-0.13
Buffalo Bills		7.14	6.63	-0.51
New England Patriots	7.39	7.07	-0.32
Houston Texans		7.61	7.50	-0.11
Seattle Seahawks	7.81	7.78	-0.04
Denver Broncos		7.89	7.93	 0.04
Arizona Cardinals	7.90	7.47	-0.43
Jacksonville Jaguars	8.02	7.96	-0.06
St. Louis Rams		8.15	7.91	-0.24
Detroit Lions		9.30	9.51	 0.21

Last December, I wrote that the Steelers had one of the best regular season defenses in NFL history. And while they led the league in adjusted yards per attempt allowed (4.13), they actually had a harder than average schedule, headlined by Philip Rivers, Tony Romo, Matt Schaub and Peyton Manning. After adjusting for strength of schedule, the Steelers' pass defense looks even stingier.

The Titans and the Bucs are good examples of why strength of schedule adjustments matter. The Titans (4.87) appeared to have a much tougher pass D than the Bucs (5.50), but that difference was entirely the product of strength of schedule. The Titans had only four games against QBs who were half an adjusted yard per attempt better than average: Matt Schaub (2x), Aaron Rodgers and Peyton Manning. Tampa faced Philip Rivers, Drew Brees (2x), Matt Ryan (2x), Jake Delhomme (2x) and Aaron Rodgers. The Titans also saw 138 passes thrown by the arms of Ken Dorsey, Rex Grossman, Jim Sorgi, Damon Huard, Brodie Croyle and Drew Henson. Tennessee had it pretty easy last year, and were not as good as their raw numbers would make you think.

What about the quarterbacks? Now that we have a ranking for each defense, we can adjust each pass attempt thrown by every QB based on the strength of the defense he faced. Quarterbacks who faced very tough schedules (and are undervalued by normal analysis) are in bold; quarterbacks who faced very easy schedules (and are overvalued by normal analysis) are in italics:

Team                    Adj     Raw      SOS
Philip Rivers		8.85	8.77	 0.08
Drew Brees		7.93	7.85	 0.08
Tony Romo		7.91	7.40	 0.51
Matt Schaub		7.87	7.61	 0.25
Matt Ryan		7.76	7.52	 0.24
Tarvaris Jackson	7.76	7.69	 0.07
Jake Delhomme		7.36	7.35	 0.00
Chad Pennington		7.27	7.81	-0.54
Kurt Warner		7.25	7.60	-0.35
Aaron Rodgers		7.23	7.49	-0.26
Peyton Manning		7.18	7.21	-0.04
Sage Rosenfels		6.94	6.33	 0.62
Jeff Garcia		6.93	7.13	-0.21
Eli Manning		6.89	6.70	 0.19
Donovan McNabb		6.85	6.80	 0.06
Joe Flacco		6.84	6.33	 0.50
Jay Cutler		6.81	6.84	-0.03
Matt Cassel		6.75	6.98	-0.24
Ben Roethlisberger	6.66	6.34	 0.33
David Garrard		6.47	6.23	 0.24
Kerry Collins		6.46	6.26	 0.20
Jason Campbell		6.44	6.39	 0.05
Seneca Wallace		6.31	6.68	-0.37
JaMarcus Russell	6.24	6.33	-0.09
Dan Orlovsky		6.09	5.55	 0.54
Shaun Hill		6.06	6.76	-0.70
Trent Edwards		6.06	6.60	-0.54
Derek Anderson		5.84	5.07	 0.77
Tyler Thigpen		5.79	5.78	 0.00
Kyle Orton		5.78	6.01	-0.22
Daunte Culpepper	5.72	5.18	 0.54
Gus Frerotte		5.71	5.72	-0.01
Jon Kitna		5.58	5.28	 0.30
J.T. O'Sullivan		5.41	6.10	-0.69
Carson Palmer		5.33	4.74	 0.59
Brett Favre		5.14	5.60	-0.46
Ryan Fitzpatrick	5.12	4.46	 0.66
Brian Griese		4.92	4.66	 0.26
Marc Bulger		4.88	5.36	-0.48
Matt Hasselbeck		3.62	4.14	-0.52
J.P. Losman		3.35	3.84	-0.48

On the surface, Chad Pennington's numbers look a bit better than Tony Romo's. But Pennington had 11 games against bottom ten pass defenses: Miami played the Rams, Cardinals, Broncos, Seahawks, Texans and all three division rivals twice. Romo faced 7 top-ten pass Ds in 13 games, as he was unlucky enough to have to play Pittsburgh, Baltimore, Green Bay, Washington (2x) and Philly (2x). After adjusting the numbers, Romo moves from 0.4 AY/A behind Pennington to over 0.6 AY/A ahead of him.

There are lots of QBs and defenses that get shuffled around after analyzing for strength of schedule. Because of that, it's important to look at these numbers -- and not the raw ones -- when you think about projections for the upcoming season. Of course, you should remember that Adjusted Yards per Attempt is not the perfect QB statistic. A complete analysis would consider sacks, fumbles, rushing contributions, and other factors. But AY/A is a good and quick way to passing strength on both sides of the ball, and these numbers help to isolate the actual best (and worst) passing QBs and defenses in the league.

Finally, let's take a look at some weather adjustments. As Doug noted when he unleashed the weather modifiers, single season weather adjustments are very "iffy." Matt Cassel' game against the Bills in week 17 was in much harsher conditions than your typical game in a moderately cold weather city in December/January. On the other hand, you can probably just dock Peyton Manning and Matt Ryan about 0.2 AY/A (or CY/P) per season. As the table below explains, Losman, McNabb and Rodgers faced (very roughly) the most difficult climates in 2008.

                        Att      Weather
J.P. Losman		104	 0.18
Donovan McNabb		571	 0.18
Aaron Rodgers		536	 0.15
Ryan Fitzpatrick	372	 0.13
Matt Cassel		516	 0.12
Derek Anderson		283	 0.07
Jason Campbell		506	 0.06
Matt Schaub		380	 0.06
Brett Favre		522	 0.06
Tyler Thigpen		420	 0.06
Kurt Warner		598	 0.05
Ben Roethlisberger	469	 0.05
David Garrard		535	 0.04
Joe Flacco		428	 0.03
Kyle Orton		465	 0.03
Matt Hasselbeck		209	 0.03
Jake Delhomme		414	 0.02
Tony Romo		450	 0.02
Jay Cutler		616	 0.01
Trent Edwards		374	 0.01
Chad Pennington		476	 0.01
Carson Palmer		129	 0.01
Jeff Garcia		376	 0.01
Sage Rosenfels		174	 0.01
Philip Rivers		478	 0.00
Shaun Hill		288	 0.00
Eli Manning		479	-0.01
Kerry Collins		415	-0.01
Brian Griese		184	-0.02
JaMarcus Russell	368	-0.02
J.T. O'Sullivan		220	-0.04
Seneca Wallace		242	-0.05
Dan Orlovsky		255	-0.09
Drew Brees		635	-0.17
Tarvaris Jackson	149	-0.19
Gus Frerotte		301	-0.19
Marc Bulger		440	-0.19
Matt Ryan		434	-0.19
Peyton Manning		555	-0.21
Daunte Culpepper	115	-0.23
Jon Kitna		120	-0.28

This entry was posted on Monday, August 24th, 2009 at 6:18 am and is filed under Statgeekery. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.