Brett Favre was the NFL’s ultimate iron man for 19 years, inspiring coaches and teammates with extraordinary toughness and thrilling fans with a daredevil’s verve and a showman’s sense of the moment.

Yet the once-irrepressible Favre never looked older or more fragile than in year No. 20. The magic of last season, and most of his brilliant career, never seemed farther away.

It had to end some time. And Favre says that time is now.

The 41-year-old quarterback sat out Minnesota’s season-ending loss to the Detroit Lions on Sunday because of a concussion, and it appears his career ended not on the field trying to rally the Vikings to another victory, but on the sideline as a third-string rookie floundered in Favre’s place.

No one — not even Brett Favre — can play forever.

“I know it’s time, and that’s OK. It is,” Favre said after the 20-13 loss. “Again, I hold no regrets, and I can’t think of too many players offhand that can walk away and say that. Individually and from a team standpoint, it was way more than I ever dreamed of.”

He also retired in 2008 with the Packers and 2009 with the Jets, only to return both times when the football bug bit him in the summer. He knows that there will be doubters again.

“I don’t know for me if it’s ever easy,” Favre said. “I’m sure throughout this year, the comment has been made that, ’We’ll wait and see in August or September’ and that’s fine. It’s time. I’m OK with it.”

There appears to be one big difference this time. Even if he did want to come back next year, would anyone want him? The Vikings are going to start over. And the market for a 42-year-old quarterback coming off one of his worst seasons — both personally and professionally — doesn’t figure to be hot.

If this indeed is the end — for real, this time — for Favre, one of the most colorful and celebrated careers in NFL history concluded with a season filled with interceptions, injuries and insults.

He threw 19 interceptions and his 69.9 quarterback rating is the lowest of his career. The Vikings sunk to the bottom of the NFC North after starting the season with Super Bowl aspirations, coach Brad Childress was fired during the season and Favre was fined $50,000 for failure to cooperate with an NFL investigation into allegations that he sent lewd photos and messages to a game-day hostess when both worked for the Jets in 2008.

Favre’s reputation took a serious hit from the humiliating scandal, which tarnished the image of one of the league’s most popular players. He declined to comment on the fine after the game.

His long-awaited union with receiver Randy Moss also was a spectacular failure and his cherished streak of 297 straight starts ended three weeks ago, with a sprained throwing shoulder making it impossible for Favre to let those famously zip-filled passes rip from his right arm.

And just for good measure, the Metrodome roof caved in to provide a perfect metaphor for Favre and the Vikings’ 2010, forcing the Vikings to play “home” games at Detroit and at the University of Minnesota’s outdoor stadium in December.

“It’s been a wonderful experience for me,” Favre said. “This year did not work out the way we would have hoped, but that’s football. I don’t regret coming back. I enjoyed my experience here.”

He was listed as doubtful against the Lions, having failed to pass the necessary tests to be cleared to play during the week. The Vikings announced that he was inactive about 80 minutes before kickoff, and Joe Webb started his second straight game at quarterback.

“He’s a guy who loves football to death. You can tell. He played up until he was 41 years old,” Webb said. “I admire him, he’s a great mentor for me. I’ll always keep in contact with him.”

The season started reluctantly, with Favre having serious reservations about coming back after having surgery on his ankle last summer. He also wondered if he could duplicate his incredible 2009 performance, which he called the best of his career.

Childress had to send three of Favre’s closest friends on the team — Ryan Longwell, Jared Allen and Steve Hutchinson — on a private plane to Hattiesburg, Miss., to coax the old man into coming back for one more shot at a Super Bowl.

But that sensational 33-touchdown, seven-interception masterpiece he put together to help the Vikings reach the NFC title game last season was doomed from the start. Injuries to his two best receivers made it difficult for Favre to get going, and that seemingly indestructible body of his finally started to break down.

“All indications, when I talk with him, and we’ve had many, many discussions — this is it,” interim coach Leslie Frazier said. “I don’t even think it’ll be an issue in the future. I don’t see any situation that’s going to change his mind. You might say, ’Well, we’ve been down that road before,” but it’s different now. Things are different, in his life and in the organization’s life as well.”

The website Deadspin published the tawdry allegations about Favre’s supposed advances on Jenn Sterger in October, and he spent the next two months sidestepping questions about it while being exposed to the kind of public humiliation that he’s never had to deal with before.

His record starts streak ended against the Giants on Dec. 13. He was knocked out of three games this season — against New England on Oct. 31 with a gaping wound on his chin, Buffalo on Dec. 5 with the shoulder injury and Chicago on Dec. 20 with the concussion — and also played through two broken bones in his foot, tendinitis in his elbow and injuries to his neck, back, ribs and calf.

Renowned for his ability to recover quickly, Favre missed three of his final four games and played a total of less than two quarters over the final five games as the Vikings fell apart.

Childress was fired after a 3-7 start and the Vikings finished 6-10, putting them in last place for the first time since 1990. Favre’s team also finished with a losing record for just the second time in his 19 years as a starter.

“One game, one season does not define me,” Favre said. “There will be people saying it’s a shame you went out that way, this and that.

“I am truly grateful for the opportunity that, by the grace of God, I got a chance to play this game and play it at a high level and I’m honored. I hope that people admired the way I played, my passion for it, because I hold no regrets.”

Assuming this is the end, Favre departs as the career leader in victories (186), yards passing (71,838), touchdown passes (508), attempts (10,169), completions (6,300) and interceptions (336). He was drafted in 1991 by Atlanta but never completed a pass for the Falcons before moving on to Green Bay, where he spent 16 seasons, won three MVP awards and led the Packers to a Super Bowl title in 1997.

After the Packers grew weary of his indecisiveness about retirement, they traded him to the Jets. He spent a forgettable season in New York before joining the Vikings in 2009.

There were a few highlights for Favre in 2010. He threw his 500th TD pass against the Jets on Oct. 11 and threw for a career-high 446 yards to rally the Vikings from a 14-point deficit with less than 5 minutes remaining to beat the Cardinals on Nov. 7.

Favre got one last victory under his belt when he won the coin toss before the game on Sunday. When the final whistle blew, Favre waved to the fans and jogged past his teammates, up the tunnel and into the locker room.

“That’s the thing every player and former player that I’ve talked to … will tell you that what you miss is the guys, the fellowship, the bus rides, locker rooms, winning and losing together, celebrating together,” Favre said. “That’s the things you’re going to miss. If I sat here and told you I would not miss that, I’d be kidding myself. From a playing standpoint, there’s nothing else left to do.”