Three-time Pro Bowl left tackle Tra Thomas is retiring. Thomas, 35, said Saturday that he has decided to leave the game because he can longer play at the level he expects from himself. He recently had arthroscopic knee surgery and he said he hasn't performed well during this camp. He signed with San Diego in June as a possible replacement for Marcus McNeill, who is holding out. "I was just watching film and I don't think I was playing as well in practice as I should be," said Thomas, who entered the NFL as a first-round pick of Philadelphia in 1998. "If I'm not playing well in practice, I'm not going to play up to my standard in a game ... I feel very good about the decision. I 'm going out on my own terms. At least, I know I gave it everything I could." He said he appreciates the chance San Diego gave him, but he thought it was best to leave the game. "I could have milked it for a year," Thomas said. "But I have too much respect for the game to do that." Source: ESPN