Favre said that the injury that required surgery on his biceps tendon and then finding out that he had a tear in his rotator cuff led him to think he shouldn't play anymore.

"I just kept thinking I didn't want to go through what I did last year," he said.

"Between three weeks ago and the phone conversation yesterday [with Childress], I talked to Dr. [James] Andrews and he assured me it wouldn't be an issue. I felt if everyone was going to take that chance, I was to."

Dr. Andrews detected a slight tear in his right rotator cuff in May while performing arthroscopic surgery on the quarterback's passing shoulder.

During practice sessions in Mississippi, Favre said that "the arm has felt, not 100 percent, but pretty good, good enough to make the throws I need to make."

That led him to decide to go for it.

"As friends and family has told me, you never know until you take the chance," he said.

Favre, who holds almost all of the NFL's career passing records, has never been much of a fan of offseason practices, though. Last summer, he ended his retirement with the Packers and forced a trade to the Jets, where he faded down the stretch amid problems with his throwing arm.

But Favre remained in regular communication with the Vikings' coaching staff the past three weeks, and a source told ESPN's Ed Werder that owner Zygi Wilf had to do very little convincing when the two met this week near Favre's home in Hattiesburg.

"He had a lot of aches and pains and they basically needed a commitment from him before he felt he was ready to play,'' a source told Werder. "He wants to be able to do the best he can do and doesn't want to disappoint them.''

Favre has been working out regularly with Oak Grove High School players in Hattiesburg, according to WDAM-TV, and has not missed a practice even after telling the Vikings he would remain retired.

The fact that the Vikings have a chance to make a deep run in the playoffs factored heavily in Favre's decision.

"I felt from my standpoint that I could offer some experience and leadership, and I have to admit through this whole process after I said no three weeks ago, sometimes I was OK with it, and other times I said. I can really help this team."

The Vikings finished training camp last week and beat Indianapolis 13-3 in their preseason opener Friday. They got a strong performance from quarterback Sage Rosenfels, who has been competing with Tarvaris Jackson for the starting job since Favre jilted the team July 28.

When Favre arrived at training camp, third-string quarterback John David Booty graciously gave him his jersey number. Booty, who had been wearing No. 4, was assigned No. 9.

Jackson and Rosenfels were a little more begrudging in handing over the starting job.

"It's not a good feeling, but you have to take it for what it's worth and try and get better from it," said Jackson, who was hoping to assert himself and live up to the label of quarterback of the future he received when coach Brad Childress drafted him in 2006.

It may be even more difficult for Rosenfels, who spent the first eight seasons of his career as a backup in Washington, Miami and Houston. When the Texans traded him to the Vikings this offseason, the 31-year-old thought he was finally getting a chance to be the man.

Now he'll have to take a seat on the bench, again.

"It's something that wasn't a total shock," said Rosenfels, who had a strong preseason debut when he completed 10 of 13 passes and led two scoring drives against the Colts on Friday. "Obviously this has been three months in the ongoing sort of thing. So for me personally, this wasn't what I was hoping for. I tried to get traded here and got traded here.

"But in my nine years this is the best football team I've ever been on. We have so much talent. If the team needs me this year, when the team needs me this year, I'm going to be ready."

The Vikings are expected to challenge for the NFC North title this season, with whoever is behind center.

Rosenfels and Jackson have had some rough moments during practice. Jackson hurt his knee, missed a few workouts and then returned, but he was out of sync last week against the Colts.

Rosenfels did well, but preseason games are tough to evaluate and Indianapolis held out all four starting defensive backs.

Linebacker Ben Leber had nothing but sympathy for two veterans he watched work so hard during the most grueling part of training camp as they tried to assume control of the team. He wasn't sure if either player could be consoled at this point.

"I don't know what you say to them," Leber said. "It's hard to sit there and say, 'Hey, keep competing.' I think it's pretty clear who is going to be the No. 1 guy. I guess you have to compete for No. 2 and it will figure itself out."

Childress sat down with all three incumbent quarterbacks on Tuesday morning before going to the airport to personally pick up Favre. He said it was "a hard conversation to have" with them all after only three weeks ago telling them they were moving on without Favre.

"But our game is about competing," Childress said. "Just like I told our team today again, whatever position you're at, you're fighting for the 53 spots on this football team. You make a huge mistake to count the number in lines or how many are we going to keep.

"The fact is we've used a couple of quarterbacks every year I've been here from an injury standpoint. I think those guys will keep their eye on what they need to do."

When the possibility of Favre joining the Vikings first arose earlier this offseason, there were reports that Jackson would request a trade.

"I never said that," Jackson said Tuesday. "I never said anything like that at all."

Rosenfels, who has missed two straight practices with a sprained right ankle, was a little more coy when asked if he would seek a trade.

"I don't know. I haven't really thought about that," Rosenfels said. "I'm just trying to get my ankle fixed right now. It's feeling pretty good for the most part but just trying to get that right. I haven't even really thought about that stuff."

Favre also could have to smooth things over with some of the veterans who reported to camp on time, were spurned by him initially, then spent the next two weeks sleeping in those uncomfortable dorm beds at Minnesota State University, Mankato and enduring two-a-day practices.

"Brett Favre is a different player. He's a Hall of Fame player," tight end Visanthe Shiancoe said. "He can kind of stretch the limits a little bit. No hard feelings. He's here. It is what it is."

For his part, Favre said he's ready to start getting to know his teammates and will ease into a leadership role when the time is right.

"Even though I've played a long time and been around and played against a lot of guys and played under a lot of coaches and against a lot of coaches, you still have to earn the respect of this team," Favre said. "What you've done in the past is great, but it means nothing here. ... You earn the respect of these guys and that's what I intend to do."

Packers coach Mike McCarthy said after practice Tuesday he was not surprised by Favre's return.

"I don't think anybody should be surprised by it," McCarthy said.

Green Bay visits Minnesota on Oct. 5, and the Packers host the Vikings on Nov. 1.

"The bottom line is it's football," Favre said. "Once you step into the huddle, I don't look at the helmets. I look at the faces and the guys will know I'm in it for the right reasons because I still love to play."

Aaron Rodgers, who inherited the starting quarterback position after Favre retired -- then unretired -- said, "I don't have a reaction. It doesn't pertain to me. It has absolutely nothing to do with me. It doesn't change anything. It has nothing to do with the Green Bay Packers."

Packers general manager Ted Thompson also didn't want any part

of the Favre situation, which caused a major distraction during the

Packers' training camp a year ago and lingered on well after Favre

was traded to the Jets.

After dodging a few questions about Favre on Tuesday, Thompson

refused to bite on a question about whether it's wise for a team to

tie its fortunes to a player with commitment issues so late in

training camp.

"You guys just try to get me in trouble," Thompson said,

smiling.

Packers linebacker Nick Barnett told the newspaper: "After all those years of not being able to hit him, do I want to hit him? Of course I want to hit him. He's an awesome guy. I wish him the best."

Information from ESPN senior NFL analyst Chris Mortensen, ESPN NFL Insider Adam Schefter, ESPN reporter Ed Werder, ESPN analyst Cris Carter, ESPN.com's Kevin Seifert and The Associated Press was used in this report.