Brian Urlacher, after 13 seasons as linebacker with the Chicago Bears, announced Wednesday that he is retiring from the NFL.

Urlacher, who turns 35 later this week, said he was honoured to spend his whole career with the Bears.

"Although I could continue playing, I'm not sure I would bring a level of performance or passion that's up to my standards. I'm proud to say that I gave all of you everything I had every time I took the field," he said in an online statement.

"I will miss this great game, but I leave it with no regrets," he added.

Urlacher wanted back with the Bears for another season, but his representatives and general manager Phil Emery could not hammer out an agreement.

Urlacher told the team's flagship radio station at the time that he was not shocked and that the offer he received was "more like an ultimatum" in which they were telling him, "Sign this contract or we are going to move on."

There were reports linking him to the Minnesota Vikings earlier this month.

Selected ninth overall in 2000 out of New Mexico, where he grew up, Urlacher immediately made an impact.

A safety with lightning speed, the six-foot-four Urlacher initially lined up at strong side linebacker for the Bears but lost the job to Roosevelt Colvin. He made the switch to middle linebacker during his first season when Barry Minter was injured and went on to become the NFL's defensive rookie of the year, the start of a long run that saw him anchor a defence that consistently ranked among the league's best.

He was voted the league's top defensive player in 2005.

Urlacher appeared in all 16 regular season games in all but three of his 13 seasons.with the Bears, who he helped lead to a Super Bowl appearance in 2006-07.

He finished with 41 ½ sacks, 22 interceptions and 12 forced fumbles.

But he clearly wasn't his old explosive self last year. The speed and quickness that allowed him to wreak havoc for years simply wasn't there.

Urlacher sprained his medial collateral ligament and partially sprained the posterior cruciate ligament in his left knee during the 2011 regular-season finale against Minnesota and hasn't been the same since then.

He barely participated in training camp, had an arthroscopic procedure in mid-August to relieve the swelling, and spent most of the season trying to regain his old form.

Then, he came up lame in coverage on the second-to-last snap of the Bears' overtime loss to Seattle in early December, an injury that ended his season and, it appears, his career.

With files from CBCSports.ca