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Pro Football Reference Blog

Rex Grossman

Posted by Chase Stuart on January 10, 2007

You may remember this blog post, where I looked at some of the worst QBs in NFL history. I used "Adjusted Yards per Attempt" as the sole statistic to rank the quarterbacks. Of course, no one metric could ever fully capture the value of a player, especially a QB. But there are some circumstances where we need to rely on one stat to analyze the data, and I believe adjusted yards per attempt is the best one to use for examining passers.

For those unfamiliar, Adjusted Yards per Attempt is calculated by taking a QB's total passing yards, adding 10 yards for every TD thrown, subtracting 45 yards for every INT thrown, and dividing by total attempts.

Rex Grossman averaged 5.26 AY/A this year, which isn't terrible, but isn't very good, either. The NFL average was 5.81, so Grossman was a below-average passer this year. But that's not what's incredibly interesting to me, about his season. Three times this season, Grossman had AY/A ratings of over 9.50, and three times this year he had AY/A in the negatives. That's pretty odd: only eleven times this season did any QB have a negative AY/A in a game (min: 10 attempts). No QB reached that level of futility twice, but Grossman did it three times, and had the two worst averages in 2006.

```
tm	wk	opp	att	yd	td	int	ay/a
C Simms 	tam	1	rav	29	133	0	3	-0.07
J Losman	buf	5	chi	27	115	1	3	-0.37
R Grossman	chi	6	crd	37	144	0	4	-0.97
K Collins	oti	2	sdg	19	57	0	2	-1.74
D Carr  	htx	15	nwe	28	127	0	4	-1.89
D Anderson	cle	16	tam	27	123	0	4	-2.11
C Pennington	nyj	5	jax	17	71	0	3	-3.76
B Johnson	min	13	chi	26	73	0	4	-4.12
J Harrington	mia	15	buf	17	20	0	2	-4.12
R Grossman	chi	13	min	19	34	0	3	-5.32
R Grossman	chi	17	gnb	12	33	0	3	-8.50
```

But there's another side to Rex, of course. Only seven quarterbacks had three or more games with an AY/A of 9.50 or greater: Peyton Manning, Ben Roethlisberger and Donovan McNabb did it four times each; Philip Rivers, Damon Huard, Drew Brees...and Rex Grossman hit that mark three times. None of those six ever had a negative AY/A, while Grossman did it three times. So is Rex the ultimate two-faced QB?

We can find out by taking the standard deviation of each QB's AY/A in every game, relative to his average AY/A for the season. (Comparing it to his average AY/A, rather than the league average, gives us a better idea of how inconsistent the player is.) So where does Rex rank?

Twenty-two QBs this year played in twelve games (or more) where they attempted 10 (or more) passes. The following list should help us figure out which QBs were the least and most consistent:

```
Player			StDev
Rex Grossman		5.74
Ben Roethlisberger	4.09
Philip Rivers		3.11
J.P. Losman		3.06
Charlie Frye		2.93
David Carr		2.89
Michael Vick		2.86
Alex Smith		2.83
Matt Hasselbeck		2.69
Brett Favre		2.61
Vince Young		2.58
Drew Brees		2.57
Steve McNair		2.47
Marc Bulger		2.37
Eli Manning		2.24
Carson Palmer		2.09
Peyton Manning		2.06
Jon Kitna		1.92
Jake Delhomme		1.79
```

Not surprisingly, Grossman tops the list, and by a wide margin. For those unfamiliar with standard deviation, what that 5.74 number means is that if Grossman's performances are normally distributed, we'd expect his AY/A in a given game to fall between -0.48 and 11.00 roughly 68% of the time. On the other hand, we'd expect Peyton Manning's AY/A in a given game to fall between 5.66 and 9.78 about 68% of the time. Obviously, Manning's performance in any given game is going to be much more predictable than Grossman's. Perhaps even more amazing is that nearly 1/3 of the time, we'd expect to see Grossman play absolutely out of his mind good (over 11.00 Y/A) or absolutely horribly bad (a negative AY/A).

So how inconsistent was Grossman? Not only is his 5.74 mark the worst this year, but it's the worse since 1995 (which is as far back as the PFR games database goes). Here are the most inconsistent QBs that threw at least ten passes in at least twelve games:

```
Name			Year	G	StDev
Ben Roethlisberger	2005	12	5.34
Chris Chandler		2001	14	4.84
Jon Kitna		2000	14	4.50
Tony Banks		1996	13	4.30
Chris Chandler		1995	13	4.09
Jay Fiedler		2003	12	3.98
Dave Brown		1996	15	3.90
Jeff Garcia		2003	13	3.85
Drew Bledsoe		1999	16	3.77
Aaron Brooks		2001	16	3.76
Kurt Warner		2001	16	3.71
Chris Miller		1995	13	3.62
Steve McNair		2001	15	3.61
Drew Bledsoe		2003	16	3.55
Kurt Warner		1999	16	3.53
Kordell Stewart		2001	16	3.53
Stan Humphries		1996	12	3.51
Jim Kelly		1996	13	3.50
```

So there you have it; Rex Grossman has been the most inconsistent quarterback in the last 12 years of NFL football. The good news for Bears fans? The second most inconsistent QB won the Super Bowl just last year. But remember, Roethlisberger led the league in AY/A in 2005, so you'd expect a bit more variation in his game totals. The higher the number is, the larger you'd expect the standard deviation to be. For Grossman's StDev to be greater than his adjusted yards per pass is mind-boggling. We don't have game data going back much farther, but I'd be surprised if there's ever been a QB as inconsistent as Rex Grossman was in 2006.

This entry was posted on Wednesday, January 10th, 2007 at 4:59 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.