Can Brett help Adrian?

One of the persistent reasons I've heard for bringing Brett Favre -- or any quality quarterback -- to the Vikings is that the threat of an improved passing game will open up more holes for Adrian Peterson (and Chester Taylor) to run through, thus improving the running game as well as the passing game. With teams forced to respect the pass more, Peterson will face fewer eight-man fronts and be poised for a spectacular year.

Putting aside the question of whether Brett Favre will improve the Vikings' passing game, I've always found this type of reasoning questionable. Certainly, on the surface, it makes sense, and you hear this logic frequently espoused by commentators and even coaches. But does a better passing game actually improve the running game? And here's another thought: Adrian Peterson has averaged 101.3 yards per game and 5.2 yards per carry during his professional career. Is it really realistic to expect that any improvement to the team will push him much over a 1,600-yard season on a consistent basis?

When you think about it, in terms of raw numbers, an improved passing game should probably decrease overall rushing numbers. After all, if your passing game is good, you should be using it a fair amount, and that's going to take carries away from your running back. The 2008 Vikings threw the ball 452 times (with 43 sacks) and an unknown number of QB scrambles, for about 500 total pass dropbacks. If they'd dropped back to pass 600 times, that would have been 100 or so fewer possibilities for Peterson and Taylor to carry the ball. That'll subtract from your rushing yards, no doubt.

I took a few stabs at this concept last year, and my admittedly amateurish results showed that a good passing game does not help the running game (or vice versa). Brian Burke over at Advanced NFL Stats has talked about a similar topic a few times, and uses what I like to call "The Princess Bride Paradox":

* Your team is very good at rushing. Thus, it should rush the ball.
* The defense knows you're good at rushing. Thus, they'll play a stout run defense.
* You know that the defense knows you're good at rushing. Thus, you'll surprise them by passing!
* The defense knows that you know that they know that you're going to try and stop the run. So you'll outsmart them by playing the pass!
* You know....

Y'know?

Brian's follow-up post used the 2007 Vikings as a specific example by asking what their optimal run-pass mix was, given their talent. His conclusion was that talent on one side of the offense (running or passing) shouldn't affect play-calling on the other side, though he did acknowledge that the passing game improved slightly when Peterson was added in 2007.

But all this still doesn't answer the basic question: Would an improved passing game help Adrian Peterson? Since he ran for 1,760 yards last year at a 4.8 yards-per-carry clip, there doesn't seem to be much that could help him. So I got to wondering, in the best seasons ever by running backs, did those backs have a strong passing game to "open up lanes" for them?

The answer: not so much. I took the top 27 single-season rushing performances -- that's every season of 1,700 or more yards -- and checked out their passing games. Here are the results:

Year	Running Back	Rush Yds	Pass Att	Pass Yds	Rating
1984	Eric Dickerson	2,105	358	2,382	65.9
2003	Jamal Lewis	2,066	415	2,517	64.7
1997	Barry Sanders	2,053	540	3,605	75.4
1998	Terrell Davis	2,008	491	3,808	93.5
1973	OJ Simpson	2,003	213	1,236	42.7
1980	Earl Campbell	1,934	463	3,271	70.4
1994	Barry Sanders	1,883	459	3,085	80.2
2003	Ahman Green	1,883	473	3,377	90.5
2005	Shaun Alexander	1,880	474	3,632	96.8
1963	Jim Brown	1,863	322	2,449	78.3
2005	Tiki Barber	1,860	558	3,762	75.7
2002	Ricky Williams	1,853	455	3,069	79.3
1977	Walter Payton	1,852	305	2,070	61.8
1998	Jamal Anderson	1,846	424	3,744	92.7
1986	Eric Dickerson	1,821	403	2,380	63.7
1975	OJ Simpson	1,817	354	2,661	80.2
2006	LaDainian Tomlinson	1,815	466	3,412	93.0
1983	Eric Dickerson	1,808	489	3,411	76.0
2006	Larry Johnson	1,789	450	3,243	84.7
1995	Emmitt Smith	1,773	494	3,741	91.7
2008	Adrian Peterson	1,760	452	3,217	81.5
1985	Marcus Allen	1,759	506	3,481	68.5
1997	Terrell Davis	1,750	513	3,704	87.4
2005	Larry Johnson	1,750	507	4,014	90.1
1985	Gerald Riggs	1,719	462	3,025	66.5
1992	Emmitt Smith	1,713	491	3,597	88.8
2000	Edgerrin James	1,709	571	4,413	94.7
1993	Average	1,855	448	3,197	80.5

The five running backs with 2,000-yard seasons had Jeff Kemp, Kyle Boller, Scott Mitchell, John Elway, and Joe Ferguson as their primary quarterbacks. Apart from Elway (who missed four games with injury and was replaced by Bubby Brister), that's a pretty sorry group.

Only eight of the 27 seasons featured quarterbacks with passer ratings of 90 or higher and the overall weighted average is 80.5 and the better entries seem to be clumped down near the bottom, with the lower rushing totals. That's not real impressive, and only four of these 27 seasons occurred before the changes to open up the passing game in 1979.

Of course, what I should really be looking at is overall rushing totals for an entire team (minus quarterback rushing numbers), but that would require more effort than I'm willing to put in :P Still, consider the following additional two seasons:

Year	Running Back	Rush Yds	Pass Att	Pass Yds	Rating
2007	C. P.	1,756	432	2,938	74.2
2008	C. P.	1,727	452	3,217	81.5

Those are a couple more excellent 1700+ yard seasons that would be added to the list above if "C. P." were a real person. He's actually the combined rushing numbers of Adrian Peterson and Chester Taylor ("Chester Peterson"), multiplied by 80% to give a reasonable number of carries (316 and 372 for 2007 and 2008, respectively) and represent that C. P. probably wouldn't be actually able to carry the ball 859 times over consecutive seasons. Again, the quarterbacking for C. P.'s team has been mediocre to poor for two seasons, yet he's put up spectacular numbers. How would adding a better quarterback improve them?

Without question, better quarterback play would improve the Minnesota Vikings as a team, though whether it would improve the running game is, I think, questionable. Even if we could somehow acquire the in-their-prime versions of Joe Montana and Jerry Rice and plant them on the '09 Vikings, Adrian Peterson would be hard-pressed to improve on his stats from the previous two years. There are just only so many plays to go around, and if the passing game is that much more improved, we should use it more.

Pacifist Viking does raise a good point, though. It might be that an improved passing game will make Peterson more consistent on a per-play basis. I brought up Barry Sanders in the discussion, as a perfect example of a player who very rarely had a good passing game to support him and could be maddeningly inconsistent on a carry-by-carry basis. Without access to play-by-play data, it'll be tough to prove/disprove this, but it's a decent enough assumption. Personally, I think consistency is overrated, but that's a topic for another post.

Based on the evidence from NFL history, though, it's hard for me to believe that an outstanding rushing season is the result of good passing from the same team. Some of this might be because, with limited resources (i.e., cap room), teams can't invest in as much. So you have a great running back and so-so QB and receivers (and a line that's better at run blocking than pass protection); all that might result in some of the disparity we see here. But when it comes to improving your running game, the most important factor, I feel, is the talent of your running back and his blockers -- not your quarterback and receivers.