Chicago Bears veteran Brian Urlacher has announced his decision to retire from the NFL after 13 seasons at the Illinois franchise.

Urlacher, who left the Bears in March, has struggled to find a new club and has cited his decline as a player as the reason to call it a day.

"After spending a lot of time this spring thinking about my NFL future, I have made a decision to retire," he wrote in a statement.

In the hours following the decision, Urlacher explained the move further on the Rich Eisen podcast.

"Honestly, I'm just not quite the same player I used to be," he said. "If I was the same player that I was three or four years ago, I think I'd still want to play, but I'm not.

"After I hurt my knee, I just haven't been able to do the same things I want to do. So, it's frustrating for me, and I don't want to do it any more."

Urlacher made a combined 1,229 tackles in his career.