"It was very tough, obviously," Favre said at a news conference after practice. "I could make a case for both playing and not playing. I think ultimately, much has been made about the three guys coming down. It was really about … the team."
Favre said the possibility of winning a Super Bowl drove him to return.
"The mental toll was really hard to deal with," he said of last year's elimination from the playoffs. "This team is a very good football team. The chances here are much greater than in other places. … From that standpoint, it has always made it easier."
Favre, who underwent surgery on his ankle in May, said he's not fully healthy, but he hasn't been fully healthy in years.
"There's nothing on me 100 percent," he said. "But I played 309 straight games, I can't complain.
"I can't promise you I'll make it through the season," he added. "I couldn't promise that when I was 21."
After Favre had helicopters tracking his every move on Tuesday as he flew from Mississippi to Minnesota, the news was expected. Kicker Ryan Longwell said on Tuesday that Favre would be playing this year.
Favre said that part of the reason he contemplated retirement this summer was that he had done so well last season.
"It was such a great year, it would be easy to say, 'Hey, can't play any better, why even try?'" he said.
Favre, who will turn 41 in October, will be playing in his 20th NFL season and his second for the Vikings. He led Minnesota to a 12-4 record last season and brought them to the NFC Championship Game. His last-minute interception, however, allowed the Saints to force overtime and eventually win the game.
Once an almost-universally liked icon, Favre has become a bit of a polarizing figure over the past few years. Once he hit his mid-30s, Favre spent his summers building "will he or won't he" suspense. He's cried at retirement announcements, ditched his longtime home of Green Bay, got out of a Jets contract by retiring and soaked up all the attention along the way.
What he's also done along the way is play quarterback at an extremely high level. He's the NFL leader in attempted and completed passes, passing yards, touchdowns and, on the other side of the spectrum, interceptions.
This offseason, he expressed concern that his injured ankle would not be able to withstand the rigors of another NFL season. After visits from his Vikings teammates this week, however, he is ready to go.
He said he hopes to play in the Vikings' second preseason game on Sunday in San Francisco.
"The bottom line is winning," he said. "I'm not here to set any records. There's nothing left for me to prove."
