Regarding his health, he told the magazine, "Playing another year probably isn't going to make a difference; the damage has already been done."
Favre is coming off a season in which he threw 33 touchdown passes and a career-low seven interceptions. He knows the odds of repeating that success, which included a trip to the NFC title game, won't be easy.
"What are the odds that I have another season like that, even if I play real well?" Favre told the magazine.
Favre reiterated how much fun he had in 2009, saying, "Before last year, I'd reached a point where I was sitting in meetings with guys 15 years younger than me thinking, ‘What the hell am I doing here?' Football became work. But last year it went back to being a game."
The Vikings, meanwhile, are preparing to enter camp with Tarvaris Jackson as their top quarterback (for the time being). Sage Rosenfels and Joe Webb, a sixth-round pick in April, also are on the depth chart.
Favre isn't expected to join the Vikings until after the team breaks training camp in Mankato on Aug. 12. Last year, he did not end his retirement to join the Vikings until after the first preseason game.
This time there has been speculation that Favre could wait to make his appearance until after the Vikings have opened the preseason with games at St. Louis and San Francisco.
The Vikings' third exhibition is Aug. 28 against Seattle and could mark Favre's only game action until the Vikings open the regular season on Sept. 9 at New Orleans.
PLAYERS TO WATCH IN TRAINING CAMP
Hot seat: The Vikings signed veteran cornerback Benny Sapp to a two-year contract extension this offseason but that doesn't mean he has a primary role nailed down. Sapp has become the Vikings' primary nickel back but will be challenged by corner Asher Allen, a third-round pick in 2009. Allen impressed the coaches with his work this offseason and figures to get a real shot to challenge Sapp.
Linebacker E.J. Henderson: Jasper Brinkley filled in admirably last season when Henderson was lost to a broken leg in December. Coach Brad Childress said Henderson is "attacking" his rehabilitation from the injury but it is optimistic to believe he'll be full speed in early August. Henderson is targeting the Sept. 9 opener against New Orleans and said he's likely to participate in most of training camp. Brinkley, though, is one of the most improved players on the defense, according to coordinator Leslie Frazier. While he's often a liability in pass coverage, he is a solid run-stuffer and might force his way onto the field on first and second downs.