PITTSBURGH — Pittsburgh Steelers All-Pro safety Troy Polamalu sprained the medial collateral ligament in his left knee late in the first half against Tennessee on Thursday night. Coach Mike Tomlin said the injury usually sidelines a player from 3 to 6 weeks.

Polamalu was injured when a Titans player fell on him as Steelers defensive end Aaron Smith blocked a 31-yard field goal attempt by Rod Bironas with about three minutes left in the half. Polamalu was attempting to pick up the ball.

Before getting hurt, Polamalu made a one-handed interception and led both teams in tackles with six.

A two-time All-Pro safety, Polamalu was chosen for the past five Pro Bowls. He is considered one of the NFL's premier defensive players.

Though Polamalu potentially could be sidelined much of the first half of the season, the injury could have been much worse — an anterior collateral ligament injury might have sidelined him the rest of the season.

Rod Woodson, the Hall of Fame cornerback, tore up his knee in the Steelers' 1995 season opener, needed major surgery and didn't return until the Super Bowl.