MIAMI -- Daunte Culpepper summed up his thoughts Thursday in two words, which ushered in the start of a new era for the former Pro Bowl quarterback.

"Farewell NFL," he wrote.

With that, a career once filled with such promise came to a most unceremonious end.

Culpepper, who starred for the Minnesota Vikings before a major knee injury in 2005 curtailed his career, announced his retirement in an e-mail to NFL Network's Adam Schefter on Thursday morning, saying he's simply grown tired of fighting for one more opportunity. The 31-year-old was the Vikings' first-round draft choice in 1999, became their full-time starter a year later, and teamed with Randy Moss to pile up yards and touchdowns at an impressive rate.

But he hurt his right knee in October 2005, never played for the Vikings again, and never seemed to return to his past level, either.

"When free agency began this year, I had a new sense of excitement about continuing to rebuild my career in the same way that I had rebuilt my knee after my catastrophic injury in 2005," Culpepper said. "Unfortunately, what I found out was that the league did not share any of the optimism about me as an unrestricted free agent that I expected. In fact, there was an overwhelming sense that there was no room for me among this year's group of quarterbacks."

The Miami Dolphins acquired him in 2006 in exchange for a second-round pick, but Culpepper played only four games before being shut down because of continued knee problems. He was sacked 21 times in those four games, and his brief stint with Miami had two compelling images:

-- Getting sacked seven times in his first home game, where fans booed him by halftime.

-- Walking off the field during minicamp in June 2007 because the Dolphins wouldn't let him play, and flanked by a team security official.

"Now that dream to get back on the field and prove everybody wrong is behind him," said Dolphins defensive lineman Vonnie Holliday, who talked to Culpepper about his ongoing comeback quest this summer. "It has to be tough. ... When he was healthy, he was definitely one of the best."

Last season, the Oakland Raiders took a shot on Culpepper, and he made five starts there, albeit only getting 5 touchdown passes in those games. And over the past few months, he tried to get any opportunity around the league, even saying just last week that he'd be willing to be Aaron Rodgers' backup in Green Bay.

There were no takers, and Culpepper saw no reason to keep waiting.

"Since I was not given a fair chance to come in and compete for a job, I would rather move on and win in other arenas of life," Culpepper said.

In Minnesota, Culpepper's decision was met with disappointment, even though he hadn't played there for years.

"Very surprising. Surprising that he hasn't gotten a job, too. Sad," Vikings safety Darren Sharper said. "Last year I didn't think he played bad in Oakland. I've seen quarterbacks that are still playing in this league today play a lot worse. ... And they still have jobs. So I don't know the reason for it."

Culpepper completed 64 percent of his passes in a nine-year career, with 142 touchdowns. The 6-foot-4, 265-pounder out of Central Florida was a three-time Pro Bowl selection, and he was at his best in 2004, when he established career-highs in yards (4,717), touchdowns (39) and passing rating (110.9).

Then came the knee injury, and it all went downhill from there, even though Culpepper -- who has served as his own agent and announced his retirement in an e-mail -- believes he can still compete.

"No matter what I did or said, there seemed to be a unified message from teams that I was not welcome to compete for one of the many jobs that were available at the quarterback position," Culpepper said.

Culpepper said, without citing anyone by name, that he was told he'd get a chance with some teams this season when other quarterbacks got injured. Friends, family members and "league personnel" also advised him, Culpepper said, to continue waiting for a chance and postponing any decision on retirement.

"If he was anywhere close to 100 percent, it would seem teams would have to take a shot at him," Holliday said. "You look at the league and you see a lot of teams don't have that high-profile, quality quarterback."

Sometime in the past six days, though, Culpepper's mind was made up.

"I want to thank my family and my fans for their unwavering belief in me as a person and a player," Culpepper said. "I embraced both the peaks and the valleys of the game and my career. I am a better person today as a direct result of the experience of playing in the NFL. I can now focus on the enjoyment of watching some of the greatest athletes in the world play the game I love without the distraction of waiting for those elusive return phone calls."

Copyright 2008 by The Associated Press