A day of surprise, a day of sadness, but ultimately a day of understanding.

To those running the Green Bay Packers football operations, no one really expected quarterback Brett Favre to retire, not after coming off a near-MVP season in which he led the team to a 13-3 record and within an eyelash of a Super Bowl appearance less than two months ago.

And it's still hard to fathom that Favre, who informed Head Coach Mike McCarthy on Monday night and General Manager Ted Thompson on Tuesday of his retirement plans, won't be quarterbacking Green Bay this fall for the first time since September of 1992.

But both Thompson and McCarthy expressed on Tuesday that they understood the future Hall of Famer's decision, considering the tremendous extent to which he cares about his play, his team, and the undying effort required at age 38 to make both as successful as possible.

"He pours everything he has into being a professional football player, everything," Thompson said. "And that is a draining exercise, and certainly those of us around it, around professional football players, understand and appreciate that."

So Favre goes out on his own terms, with essentially every meaningful career passing record, still able to play at a high level and with teammates and a legion of fans wanting him to return.

But having expressed to McCarthy that he's "mentally tired" of all the preparation - some of it monotonous, some of it truly taxing - to be able to play another season, it seemed to Favre to be time for the next stage of his life, whatever that may be.

"Mentally tired was the constant," said McCarthy, who has spoken to Favre roughly weekly since the season ended with the overtime loss to the New York Giants in the NFC Championship.

"Last week's conversation really was a very good analogy of what he goes through. We talked about practice one day for about 20 minutes on the phone - the importance of the quarterback at practice, the importance of how he needs to keep his tempo at a very high level, a lot of little things that quarterbacks have to do that I don't think even his teammates are aware of. It's just the combination of the little things day in and day out that kind of wears on him."

McCarthy's regular conversations with Favre ran the gamut, from talking idly about the weather, to discussing all the pros and cons of continuing to play, to reflecting on how important it was to Favre for his youngest daughter, Breleigh, to see him playing championship-caliber football.

McCarthy said Favre first mentioned the word "retirement" when they talked last Thursday, but even then the head coach thought his quarterback was still coming back.

Ultimately the decision, though, was not about the state of the team, the makeup of the roster, or the belief in his abilities. It was about whether Favre could dedicate himself fully to the work required to live up to his own standards of elite play, even if millions of devoted fans would take Favre at less than his MVP-best for another year or two.

"Brett's a professional football player, one of the finest if not the finest that I've ever seen," Thompson said. "He wants to know a couple of things. Do you still want me, and can I still play? Obviously both Mike and I were very positive in that regard and said definitely we do.

"After having said that, then there are other factors that weigh into his decision-making process, and like I say, it's a very complicated thing, especially (for) one that has the experience and has played for such a long time at such a high level and has those expectations all the time."

To Favre, whose only public comments Tuesday came via a voice-mail message left with ESPN reporter Chris Mortensen, anything less than a Super Bowl championship would not be worth the effort it would take to play an 18th season in the NFL and 17th in Green Bay.

Favre clearly gave that effort in 2007, and by no means was he satisfied with the outcome. But perhaps in the end he knew either that was the most he could truly give, or that another run under self-induced all-or-nothing pressure would be too much to bear, or both.

{sportsad300}"His daily preparation was outstanding, his weekly preparation was outstanding," McCarthy said of this past season. "I think that would be normal of any champion to push himself to the limits to win another championship. Using the word stress or however you want to describe it, I think a better word to describe Brett is passion. He's an extremely passionate person, and you could see it in his preparation and you always saw it in his performance on the field."

That performance transcended an unforgettable era, whose memories were savored by many on Tuesday. From his no-timeouts-left diving score to qualify for the playoffs in the final game at Milwaukee County Stadium in 1994 to his helmet-raised sprint around the New Orleans Superdome after a first-quarter TD pass in Super Bowl XXXI to his first-play-of-overtime game-winning 82-yard heave on a Monday night in Denver this past October, and always amidst a backdrop of personal trials and tragedy, Favre captured the hearts of generations of fans with his dramatics and triumphs.

"Quite frankly, I think it's the little boy in all of us," Thompson said. "I think he plays the game like you would if you were in a backyard and you were wearing Wrangler jeans. He loves to play the game. He loves the competition. I can't say he loves getting hit, but he's OK with it. He understands that's part of the game. He's never been a fancy-pants quarterback that doesn't like to mix it up. He likes to play the game, and I think he appreciates the people who play the game alongside of him. And I think people can relate to that."

So with that, the Packers move on to the Aaron Rodgers era, but that's a topic for another day. For now there's an inescapable void, both within the leadership of the Green Bay Packers and within the hearts of fans everywhere, that will be difficult if not impossible to fill, but one that at the same time is marveled at for its magnitude.

"I know the fans are absolutely devastated today," Thompson said. "The Packers will move forward, but certainly we've all been blessed to see this man play this game the way he played it."