Pro Bowl safety Troy Polamalu is expected to come back for the Steelers' game against the Eagles on Sunday after missing the past two games with a calf injury.

Polamalu will significantly improve a defense that has struggled to make plays this year. But Polamalu has to make sure his return is not a cameo appearance.

"[The calf injury] may not be particularly serious for what it represents as far as the actual damage but it may hinder your ability to function," said Stephania Bell, ESPN's injury expert. "For a guy like Polamalu, just watching him, he's a bouncy guy. He's always bouncing on his toes and he springs forward. If you have an ailment there, it's going to be really easy to set it back. Not only do you have the inability to function or push off well, you run the risk of it being a bigger tear and a bigger injury, knocking you out for multiple weeks."

Polamalu said he injured his right calf the week leading up to the season opener in Denver. The injury was aggravated in the game.

What makes Polamalu's injury worth monitoring is it's the same calf he hurt in the playoffs last season. A tender right calf kept him out of practice leading up to the divisional playoff game at Denver.

Since the start of the 2007 season, the Steelers are 9-10 without Polamalu.