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PI Finds: Should Philip Rivers Have Won More Games?

Posted by Neil Paine on November 5, 2010

Using the PFR Play Index's Player Season Finder, you can run custom individual leaderboards across multiple seasons. For instance, here are the NFL leaders in Adjusted Yards per Attempt over the past three years:

Rk Player From To Tm G Cmp Att Yds TD Int AY/A
1 Philip Rivers 2008 2010 SDG 40 827 1270 10912 77 27 8.85
2 Drew Brees 2008 2010 NOR 39 1010 1480 11791 84 39 7.92
3 Aaron Rodgers 2008 2010 GNB 40 856 1346 10483 70 29 7.86
4 Tony Romo 2008 2010 DAL 35 771 1213 9536 63 30 7.79
5 Matt Schaub 2008 2010 HTX 34 796 1198 9552 54 31 7.71
6 Tom Brady 2008 2010 NWE 24 525 801 6076 40 17 7.63
7 Peyton Manning 2008 2010 CLT 39 961 1425 10686 75 30 7.60
8 Ben Roethlisberger 2008 2010 PIT 34 670 1057 8383 48 29 7.60
9 Kurt Warner 2008 2009 CRD 31 740 1111 8336 56 28 7.38
10 Donovan McNabb 2008 2010 TOT 38 771 1291 9440 52 29 7.11

As you can see, the leader (by far) is San Diego's Philip Rivers. In fact, 10th-ranked McNabb is closer to #2 Brees than Brees is to Rivers!

Statistically, it's tough to find a QB since 2008 who can touch Rivers. However, his team hasn't enjoyed the same lofty success: the Chargers are 24-16 over the past 3 years -- a respectable record, but one seemingly out of place next to Rivers' gaudy passing numbers. This disconnect between individual accomplishments and team performance has haunted many a quarterback in the past, and is now is the main reason Rivers isn't held up in the same group as Brady, Manning, Roethlisberger, and Brees as a quarterback. QBs are supposed to win, we're told, not amass seemingly empty stats.

But has Rivers really won that much less than we should have expected from his numbers? To answer this question, I went to the PFR Team Game Finder, sorted by passing yards, and collected every team game from 2008-2010. I calculated the Adjusted Yards per Attempt formula for each team game, and then ran a logistic regression between AY/A and whether the team won in a given game. The result of regression was the following equation, which tells us how often a team should expect to win based on their QB's AY/A in the game:

Win Probability ~ 1 / (1 + EXP(2.70534 - 0.412827*AY/A))

This means that if your QB posts a 6.55 AY/A in a game, you should expect to win half of the time; if he posts an AY/A of 9.22, you can expect to win 75% of the time.

To finish the study, I went to Rivers' game log page and ran the AY/A numbers on all of his 2008-10 games, calculating his expected winning % in each:

Year G# Date Age Tm Opp W Cmp Att Yds TD Int AY/A p(W)
2008 1 9/7/2008 26-274 SDG CAR 0 17 27 217 3 0 10.26 0.822
2008 2 9/14/2008 26-281 SDG @ DEN 0 21 33 377 3 1 11.88 0.900
2008 3 9/22/2008 26-289 SDG NYJ 1 19 25 250 3 1 10.60 0.842
2008 4 9/28/2008 26-295 SDG @ OAK 1 14 25 180 1 2 4.40 0.291
2008 5 10/5/2008 26-302 SDG @ MIA 0 13 28 159 1 0 6.39 0.483
2008 6 10/12/2008 26-309 SDG NWE 1 18 27 306 3 0 13.56 0.947
2008 7 10/19/2008 26-316 SDG @ BUF 0 22 29 208 2 1 7.00 0.546
2008 8 10/26/2008 26-323 SDG @ NOR 0 25 40 341 3 1 8.90 0.725
2008 9 11/9/2008 26-337 SDG KAN 1 27 36 316 2 2 7.39 0.585
2008 10 11/16/2008 26-344 SDG @ PIT 0 15 26 164 0 2 2.85 0.178
2008 11 11/23/2008 26-351 SDG IND 0 24 31 288 2 0 10.58 0.841
2008 12 11/30/2008 26-358 SDG ATL 0 17 30 149 0 0 4.97 0.342
2008 13 12/4/2008 26-362 SDG OAK 1 10 22 214 3 0 12.45 0.920
2008 14 12/14/2008 27-006 SDG @ KAN 1 34 48 346 2 1 7.10 0.557
2008 15 12/21/2008 27-013 SDG @ TAM 1 21 31 287 4 0 11.84 0.899
2008 16 12/28/2008 27-020 SDG DEN 1 15 20 207 2 0 12.35 0.916
2009 1 9/14/2009 27-280 SDG @ OAK 1 24 36 252 1 1 6.31 0.474
2009 2 9/20/2009 27-286 SDG BAL 0 25 45 436 2 2 8.58 0.698
2009 3 9/27/2009 27-293 SDG MIA 1 18 33 303 0 0 9.18 0.747
2009 4 10/4/2009 27-300 SDG @ PIT 0 21 36 254 3 0 8.72 0.710
2009 5 10/19/2009 27-315 SDG DEN 0 20 33 274 1 0 8.91 0.726
2009 6 10/25/2009 27-321 SDG @ KAN 1 18 30 268 3 0 10.93 0.859
2009 7 11/1/2009 27-328 SDG OAK 1 16 25 249 1 1 8.96 0.730
2009 8 11/8/2009 27-335 SDG @ NYG 1 24 36 209 3 2 4.97 0.342
2009 9 11/15/2009 27-342 SDG PHI 1 20 25 231 2 0 10.84 0.854
2009 10 11/22/2009 27-349 SDG @ DEN 1 17 22 145 1 0 7.50 0.596
2009 11 11/29/2009 27-356 SDG KAN 1 21 28 317 2 0 12.75 0.928
2009 12 12/6/2009 27-363 SDG @ CLE 1 18 25 373 2 0 16.52 0.984
2009 13 12/13/2009 28-005 SDG @ DAL 1 21 32 272 1 1 7.72 0.618
2009 14 12/20/2009 28-012 SDG CIN 1 24 38 308 3 2 7.32 0.578
2009 15 12/25/2009 28-017 SDG @ TEN 1 21 27 264 2 0 11.26 0.875
2009 16 1/3/2010 28-026 SDG WAS 1 9 15 99 1 0 7.93 0.639
2010 1 9/13/2010 28-279 SDG @ KAN 0 22 39 298 2 0 8.67 0.705
2010 2 9/19/2010 28-285 SDG JAX 1 22 29 334 3 2 10.48 0.835
2010 3 9/26/2010 28-292 SDG @ SEA 0 29 53 455 2 2 7.64 0.610
2010 4 10/3/2010 28-299 SDG ARI 1 15 20 241 2 0 14.05 0.957
2010 5 10/10/2010 28-306 SDG @ OAK 0 27 42 431 2 0 11.21 0.873
2010 6 10/17/2010 28-313 SDG @ STL 0 22 37 249 1 1 6.05 0.449
2010 7 10/24/2010 28-320 SDG NWE 0 34 50 336 1 1 6.22 0.466
2010 8 10/31/2010 28-327 SDG TEN 1 27 36 305 2 1 8.33 0.676
Total 24 827 1270 10912 77 27 8.85 27.7

Adding up the expected win values of each game, we would have expected Rivers to win 27.7 of those 40 games, while in reality he won 24. Four extra wins in 2½ years can certainly make a big difference in playoff seedings, etc., but it's probably not as huge a difference as you might have expected, given that San Diego was a .600 team and Rivers has statistically been the top QB in the league by a wide margin. And even if San Diego's record did reflect Rivers' true ability, we would expect the QB of a .600 team to have an AY/A of 7.54, which still would have ranked 9th over the past 3 years.

The point is that while quarterback play is important, there are so many other areas of the game that can impact a team's W-L record. Winning 24 out of 40 games, like Rivers has, is actually what you'd expect from one of the league's elite quarterbacks. If you win more than that, it likely says a lot more about your teammates and coaching staff than anything you have done.

This entry was posted on Friday, November 5th, 2010 at 1:54 pm and is filed under PI Finds, Play Index, Quarterbacks, Statgeekery. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.