Brett Favre's 2008-2009 average:
353-526.5 (67%), 3,837 yards, 27.5 TDs, 14.5 INTs
It's stupidly simple, but if you come back to read this blog post in January (and why on earth wouldn't you?), I think you'll see Brett Favre's numbers pretty close to the line above. Interestingly, this is almost identical to Favre's 2007 season (356-535, 66.5%, 4,155 yards, 28 TDs, 15 INTs).
Given the potential of the Vikings' running game, defense, and special teams, I would be ecstatic with those numbers. If Favre produces like that, the Vikings win 10+ games and compete for the Super Bowl.
Back at practice (Vikings.com).
At the front page of Vikings.com, you can watch a neat little highlight video of Favre from 2009 (which also serves as a reminder how good some of the Viking WRs are).