Friday, June 26, 2009

Brett & Adrian, Part 2

After my last post, Peter posited (oof -- say that five times fast!) that a strong passing game could help Adrian Peterson's average yards per carry and/or his consistency in getting positive yards with every carry. Neither of these are new ideas, as I explained in that post, referencing Pacifist Viking's post and my own previous posts on correlation. I thought it might be a good idea to revisit and possibly add to that information.

First, a warning: I am not a professional statistician or nearly as smart about this kind of stuff as this guy. So, I'm fulling willing to admit that I'm a hack playing around with mathematical concepts that, even if I don't fully understand how they work, I understand what their results signify (assuming I'm using them right).

I do have a pretty good head for numbers, though, and a willingness to give facts more weight than beliefs and adages. And the belief that we continue to hear -- not just from the pro-Brett Favre crowd, but from pretty much any team with a good running back and shaky quarterback situation -- is that a good passing game will help the running game. The argument of eight-in-the-box versus seven-in-the-box and a good passer "opening up running lanes" is posited by amateurs and professionals alike.

Problem is, the numbers don't seem to bear it out.

If Peter's principle (heh) were true, we'd expect that good passing numbers would result in high average rushing gain. As I pointed out a while back, that's not the case, at least using the stats from the 2008 season.

Pass Total/Run Average Correlation: -0.0956

Correlation, if you'll recall, is always between -1 and 1. The closer you are to 1, the closer the relationship between the two sets of data. A positive correlation (0 to 1) indicates a positive relationship, while a negative correlation (-1 to 0) indicates a negative relationship.

Even with the slight negative correlation, the absolute value of the correlation -- less than 0.1 -- is insignificant enough to be practically meaningless. Thus, according to the 2008 data, there is virtually no correlation between total passing yards and rushing average. A strong passing game does not help out the running game.

But raw passing yards (minus sacks) isn't the only measure of a team's success in passing. Just throwing for a bunch of yards doesn't necessarily make you a good pasisng team. What about the various rate stats?

Passer Rating/Run Average Correlation: -0.105
Adusted Net Yards Per Attempt/Run Average Correlation: -0.010

Again, both results are inconclusive, and it would be harder to have less of a correlation than the ANYA/Run average result (actually -0.00954)! Again, this seems to support the notion that there's no correlation between passing efficiency -- by any measure -- and rushing average.

Of course, I'm still just using one year's worth of data. It takes me a while to compile all the data, so I'll only run a couple more years, 2006 and 2007. The three-year data is presented in the chart below:

YearPass Total/Run AvPass Rate/Run AvANYA/Run Av

All three correlations grade out poorly, at least in terms of supporting the theory that passing helps running, and using the fairly small sample size of three seasons. In fact, the original hypothesis -- that a lot of passing yards helps improve a team's average yards per attempt -- seems to have a rather significant negative correlation, meaning that one somewhat implies the opposite of the other (though the direction of the correlation cannot be discerned).

I think this is a case of people trying to sound smarter than they are (like when they say that, despite the glitter and hype of passing games that the way to win is to "run the ball and stop the run") and attributing more importance than is warranted to a "hidden" part of the game. I think it's much simpler than that: Teams that are good at passing pass the ball and so they have better passing numbers than rushing numbers. Teams that are good at running run the ball and so have better rushing numbers than passing numbers. That's it. If it is true that running well opens up the passing game, then the passing numbers will look better and the strong-running team will look more balanced, and vice versa.

In the end, I think that, if you want to be a better running team, improve the parts of your team directly related to your running game: your tailback, fullback, offensive lineman/tight ends/receivers who can run block, etc. Improving the quarterback doesn't really help the running game.

(There is, of course, the question of running back consistency, on a per-carry basis that, without per-carry stats, I can't prove or disprove, but the notion of it strikes me as fishy for two reasons: 1. There's no proof that it will help and it sounds like just another platitude to help us accept the unacceptable; and 2. It's based on the notion that Peterson is that type of "boom-or-bust" running back, which is only prevalent because he played that way in his last two games, while ignoring his previous 28.)

All this doesn't mean that a good quarterback doesn't help a team. I'd be delighted if Drew Brees or Peyton Manning somehow wound up on the Vikings, and it would clearly improve the team, but not because it would make Adrian Peterson look better. But the notion that Brett Favre, or any other quarterback, will make Peterson's life easier is, in my opinion, just another way to make us feel better about accepting ol' #4 as our starting quarterback.


pacifist viking said...

Actually, season-long numbers bear evidence that Peterson has been a boom-or-bust back. According to Football Outsiders, his success rate (which measures the percentage of successful runs vs. unsuccessful runs) was 46%, just 23rd in the league. The numbers suggest he does get stuffed at the line a lot.

I think this is, at least partly, a result of playing with a minimal passing threat. AP is good enough to gain his yards even when the defense focuses on stopping him; however, when the defense is willing to regularly devote eight players to the box, that would seem to increase the likelihood the RB gets stuffed at the line.

I am not that with a better passing threat, AP's yards per carry would increase dramatically. I would just hope for more 3, 4, and 5 yard gains. That type of consistency would certainly help the Vikings move the ball down the field: a boom-and-bust running game puts an offense in a lot more second-and-long and third-and-long situations (which are particularly difficult when your big weakness is that passing game). I hope a threat of a passing game would mean more 3-4 yard runs on first down, and fewer 0-1 yard runs. After all, if I remember correctly, FO ranked the 2007 Patriot running game as the most successful. I have a hard time believing that is because the Patriot RBs were as good as AP and Chester Taylor that year--I find it more likely that with Brady, Moss, and Welker spreading the field, the Patriot RBs had a lot more room to gain positive yards on every play.

I do think it's possible Sage Rosenfels would provide the very same passing threat, if not better, that Brett Favre could at this point. I'm not a strong proponent of Favre--just a strong proponent of developing a good passing game. That's an end in itself, of course, but I do think it would contribute to a more consistent running game, too.

Jason said...

I'd forgotten about the FO take on Peterson's consistency -- you're probably right on that count. I guess the next step is to correlate some of those numbers to teams' passing efficiencies. Is AP inconsistent because of his poor passing game or just because that's the type of player he is?

And I agree that, at this stage in their careers, Favre and Rosenfels are just about the same kind of player: "gunslingers" who are just as likely to break your heart as they are to come up with the big play.

Darren Campbell said...

Meant to comment on Part 1 but didn't get around to it. I think you're quite right to question how much better Peterson would be if the Vikings improved their passing game. A.P. is not some alien lifeform, although sometimes I wonder.

I think the main benefit Peterson would get from an improved passing game is that he won't get used as much. He had over 350 carries last year. That's too many. If the Vikings keep giving him the ball at that rate, a potential 10-year career could turn into six. I'd like to see him around the 280-290 range. But that only happens if the Vikes somehow learn to pass the ball.

I also wonder how much more consistent Peterson is going to become with a (slightly) better passing attack. I think Peterson is capable of being more consistent. But I also think that given what Peterson has accomplished in two seasons, he'll always be the player opposing team's focus on stopping. So I don't think Peterson will stop seeing eight or nine-man fronts unless the Vikings develop a 1998-type passing attack or his skills fade. We might just have to get used to this 1,0, -1, 2, 2, 63, pattern.

Peter said...

It's tough to reconcile common sense and contradictory numbers. It just seems right that a passing game that commands respect from opposing defenses would benefit the RBs, but as you've aptly pointed out, the correlations simply aren't there.

Other variables come into play (as always with football): did good passing teams spend money/picks on QBs and WRs and thus have less leftover for their running game? Do passing teams focus on O-lineman that excel in protection (and therefore are less likely to excel in run-blocking?)

What would be nice is if we could line up several different QB-WR-RB combinations against one average defense mulitple times.

Brees/Moss/Peterson with O-line A vs. generic defense. Go. Brees/Moss/Maroney with O-line A vs. generic defense. Go. Brees/Berrian/Peterson with O-line A... etc. Repeat all with O-line B. Go.

crunch THOSE and see what you get. (of course, we can't. that's why predicting this game is so much fun!)