DETROIT (Reuters) - Record-breaking quarterback Brett Favre sat out the final game of what he has called his last NFL season on Sunday and then said he knew it finally was time to walk away.

After watching from the sidelines with lingering effects of a concussion while his Minnesota Vikings capped a disappointing season with a 20-13 loss to the Detroit Lions, Favre suggested the risk of injury was a factor in his decision.

The 41-year-old quarterback has come out of retirement twice before, but after 20 seasons in the NFL the career record holder in nearly every major statistical category for passing simply said it was time.

"I hold no regrets, and I can't think of too many players off hand that can walk away and say that," said Favre. "I played with some great, great teammates over the years and was honored to play with them. And I just know it's time."

Despite his advancing years, Favre had one of the best statistical seasons of his career in 2009, throwing for over 4,200 yards, 33 touchdowns and only seven interceptions and led the Vikings to the NFC Championship game.

Minnesota lost that game to the New Orleans Saints but his decision to come back for a shot at reaching what would have been his third Super Bowl proved to be ill-fated.

The Vikings struggled and Favre looked a shadow of the player who had enjoyed so much success a year earlier.

He threw for 2,509 yards and 11 touchdowns, the lowest totals since his rookie year, when he played just two games.

"This year did not work out the way that we would have hoped, but that's football, and I don't regret coming back. I enjoyed my experience here," said Favre.

He also said that he understood that some fans would be skeptical of his decision being truly final.

"I don't know if, for me, it's ever easy. I'm sure throughout this year the comment has been made that we'll wait and see in August or September. But it's time," said Favre.

"I'm OK with it. It's never easy, in my opinion, it's never easy for any player. But people will ... say 'wait and see', but that's OK."

Should this prove to be the end of his career it will be at the end of a season which was riddled with interceptions and mistakes but also tinged with scandal.

Favre was fined $50,000 by the NFL earlier this week for not cooperating with an investigation into allegations he sent lewd messages to a female employee of the New York Jets when he played with the club in 2008.

But Favre will be remembered longer for his series of records.

Favre is a three-time winner of the NFL's most valuable player award and holds most major records for a quarterback, including career touchdowns, passing yards and wins.

"It's been a wonderful ride for me. One game, one season does not define me. They will be saying, 'Hey, it's a shame he went out that way' or this or that," said Favre.

"I am truly grateful for the opportunity. By the grace of God, I got a chance to play this game and play it at a high level."

(Reporting by Simon Evans in Miami; Editing by Frank Pingue)