The Carolina Panthers will be without their top running back a couple of weeks _ and possibly longer.
Coach Ron Rivera said Jonathan Stewart would miss "at least a week or two" after injuring his right hamstring Sunday in the first quarter against San Francisco.
Stewart underwent an MRI on Monday morning, although Rivera said he hadn't heard the results yet.
"We'll see how severe," Rivera said. "He said he felt pretty good walking around when I ran into him just a second ago. He literally just got back from the MRI."
Fozzy Whittaker rushed for 100 yards on 16 carries after Stewart left the win against the 49ers.
Rivera said he's confident in the backfield committee of Whittaker, Mike Tolbert and Cameron Artis-Payne in Stewart's absence. But Rivera left open the possibility of bringing in a free agent back if Stewart is out for an extended period.
Stewart was injured with six minutes left in the opening quarter when the 49ers got good penetration up the middle. Stewart ran outside and his right cleat seemed to stick in the ground just as he was swarmed over by three defenders.
The Panthers, who had Artis-Payne on the inactives list, were down to one back briefly in the second quarter when Whittaker was evaluated for a concussion. But Whittaker was cleared and ended up posting his first 100-yard rushing game since he was a senior in high school.
Rivera said he was a little nervous when Stewart and Whittaker left in short succession.
"We were fortunate enough that we're deep at that position because Tolbert was the next man up," Rivera said. "That's the unfortunate part of this game is somebody's going to get nicked and hopefully it's nothing serious."
Rivera said backup safety Dean Marlowe aggravated his hamstring injury against the 49ers, adding "that didn't sound good, either."
