Fua and McClain were both third-round selections in the 2011 NFL Draft and have been starters since Week 1. Fua suffered a significant right hamstring strain prior to Sunday's game against Tampa Bay and didn't play. McClain sprained his left knee during the first half and did not return.
It's unclear at this point if either player will need surgery.
The Panthers signed free-agent defensive tackle Ogemdi Nwagbuo and added defensive tackle Jason Shirley from the practice squad, and also signed former North Carolina State defensive tackle DeMario Pressley to the practice squad.
The Panthers have lost 14 players to injured reserve this season -- seven on each side of the ball.
Copyright 2011 by The Associated Press.