Adrian Peterson in a post-Favre era

How would the absence of Brett Favre affect Adrian Peterson this season?

Brett Favre is gone. Maybe.

As of this writing, the Minneapolis Star-Tribune reports that Favre appears ready to inform the Vikings that he won't be returning for his 20th season, much to the dismay of us folks at ESPN Fantasy. You see, after a couple consecutive years of hemming and hawing about Favre and the value he might or might not bestow upon his prospective teammates, we'd chilled out quite a bit this summer. We assumed -- as did most of the NFL world -- that Favre would be back to try and push the Vikings over the top after his wildly successful 2009 campaign. For the moment, though, that appears not to be the case.

You'll read lots of stuff about what this would do (if it's true) to the Vikings' potential as a Super Bowl contender (it ain't good) and, fantasy-wise, what it would do to Minnesota's impressive group of pass catchers.

But what about the most important guy in purple? What about Adrian Peterson?

I wrote a relatively in-depth piece back in June about why I considered Peterson the best candidate to go No. 1 overall in fantasy drafts this year, over Chris Johnson. (That was written in a world where Favre was still Peterson's quarterback.) At the time, Peterson over Johnson was a minority opinion, but now I'll wager that there are some folks whose projections for Peterson have actually gone up based on this news. I wouldn't be surprised to see some folks vault Peterson over Johnson precisely because AP has now become the best-by-a-mile weapon in Minnesota again, if Tarvaris Jackson is indeed under center. The Vikings will (goes the argument) have to ride Peterson even more, so his numbers will rise from what they were in a Favre-laden world.

I'm not automatically buying that. This sounds suspiciously like the kind of "crutch argument" I talked about in this recent piece. Let's be clear: Because a team's quarterback situation takes a presumptive hit doesn't automatically mean the running game takes an uptick. It could mean that. It could also mean that defenses fear the new quarterback less, load up the box and prevent the running back from producing what he would've produced with a better quarterback in place. Is this the situation with Peterson, if Favre is indeed gone?

Well, let's do some research. We've seen AP in a Tarvaris world. In '07 and '08 combined, Jackson started 17 games and Peterson played in 15 of them. All told, Peterson has played in 31 games where Jackson didn't start. Here's how his numbers compare.

Adrian Peterson

OK, that's interesting, and a bit unexpected. On a per-game basis, Peterson has actually been a better fantasy player with Jackson than without him. That's not a conclusive argument, because while Favre was an obvious upgrade over Jackson last year, I don't think it's definitely true that Gus Frerotte, Kelly Holcomb and Brooks Bollinger were even at Jackson's level. If we look at Peterson with Jackson and with Favre, we get another angle on this picture.

Adrian Peterson

Still, this isn't as damning as I expected it to be. Now I do think it's fair to make the argument that Peterson is deeper into his career now and maybe has lost a little of the ridiculous explosiveness that marked his first couple of seasons. Expecting him to be exactly the same player in 2010 that he was in '07 and '08 might be asking too much. Maybe today's Peterson wouldn't have produced quite so well in those Jackson starts two or three years ago. Still, the dude is 25. I don't find that argument particularly compelling.

I don't have a crystal ball. I can't promise that, if he's really going to be the quarterback, Jackson won't be so horrible that the Vikings completely fall apart and everyone on that roster loses tons of fantasy value. Heck, it's hard not to argue that the Vikings' passing game would take a massive hit. While I'm not ready to say that a proposed switch from Favre to Jackson helps Peterson (as the crutch argument might), I'm rather surprised to admit that I don't think it would hurt Peterson that badly, either. Those who've argued against Peterson in the top spot have used a few compelling arguments: the Minnesota offensive line is aging, Peterson's per-carry production is declining and those 14 short-yardage touchdowns from '09 aren't likely to repeat. To varying degrees, I agree with (and worry about) all of those arguments, but I'm starting to believe the quarterback isn't going to completely sink him, because his production has been pretty darned consistent no matter who's been under center. If Favre really is gone, I don't think it's more ammunition for the AP doubters.

If Favre is really retiring, my gut tells me to downgrade Peterson a bit, but the numbers say to be a bit more circumspect. In the end, I'll split the difference. I think I'd still take Peterson over Johnson in a Favre-less world, but for the first time this summer, I'm officially wavering. I want to see what the rest of training camp and the exhibition season bring. I'm close to shuffling my top two spots. But for the moment, I'm holding off.

Christopher Harris is a fantasy analyst for ESPN.com. He is a six-time Fantasy Sports Writing Association award winner. You can ask him questions at www.facebook.com/writerboy and follow him at www.twitter.com/thewriterboy.