Stewart first complained of the injury two weeks ago. He played in Carolina's win over Arizona on Oct. 26, but was held to 10 yards on eight carries.

The Panthers were off last week, but the injury has kept Stewart sidelined. His status for Sunday's game at Oakland is uncertain.

"It's a sharp pain in my heel," Stewart said. "I have to run the ball and it hurts every time I press off on it."

Stewart, Carolina's first-round pick, has been splitting carries with veteran DeAngelo Williams. Stewart has rushed for 362 yards and a team-best five touchdowns.

"It's day to day," coach John Fox said. "But any time you don't have a guy out there it's always a concern."

The Panthers had better news with their offensive line. Center Ryan Kalil and right tackle Jeff Otah practiced for a second straight day and are expected to start against the Raiders. Kalil has missed the past three game and Otah the past four with right ankle injuries.

Reserve defensive tackle Darwin Walker missed practice with a sore neck. Walker has not played or practiced since being in a car accident two blocks from Bank of America Stadium the day before the Cardinals game.

Walker said Thursday that a woman ran a red light and he T-boned her car. The impact totaled Walker's car.

"It was like a super-hard hit on the field," Walker said. "My neck still hasn't recovered."