CHARLOTTE, N.C. — Carolina Panthers rookie running back Jonathan Stewart missed his second straight practice today and was in a walking boot to protect his sore left heel.

Panthers coach John Fox said 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.

"To be honest with you he's not really sure when he did it," Fox said. "It just started hurting. He played in the game fine. We'll kind of just wait and see."

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