DENVER (AP) _ The surgical count continues to climb for Denver Broncos offensive lineman Mark Schlereth.

Schlereth was scheduled to have left knee surgery Tuesday, marking the 29th procedure of his career _ the 15th on his left knee and the third since July.

Schlereth, who has hinted at retirement after 12 NFL seasons, was placed on injured reserve last week. He missed two games after arthroscopic surgery on Oct. 16, and did not finish Denver's game against Oakland last Monday.

Denver's bout with injuries has extended well beyond Schlereth.

The Broncos have played six games without starting running back Terrell Davis, who is still bothered by pain in his lower left leg, and quarterback Brian Griese is out at least two more weeks with a separated shoulder.

Cornerback Ray Crockett was the latest casualty. He is expected to be sidelined at least four weeks after tearing his left hamstring Sunday.

Broncos coach Mike Shanahan said he planned to sign a defensive back later this week.