Safety Troy Polamalu intercepts a pass intended for Tennessee's Kenny Britt in the Steelers' opening-night win Thursday. Polamalu suffered a knee injury in the first half and could miss three to six weeks.

PITTSBURGH — Pittsburgh Steelers All-Pro safety Troy Polamalu sprained the medial collateral ligament in his left knee late in the first half of their 13-10 overtime victory against Tennessee Thursday night. Coach Mike Tomlin said the injury usually sidelines a player from 3 to 6 weeks.

"They are reading the scans and so forth," Tomlin said. "It is speculation (how long Polamalu will be out) at this point."

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.

Tomlin said there is a chance the injury could be worse once further tests are run.

"I'm sure there's a possibility of it, but I don't have any concrete evident that there is anything more than that," Tomlin said.

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 put him out 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.