EAST RUTHERFORD, N.J. -- Carolina Panthers running back Jonathan Stewart injured his right ankle late in the first half of the team's 17-12 preseason win over the New York Jets on Sunday night.

Stewart did not return to the game. Afterwards, Panthers head coach Ron Rivera said X-rays "were completely negative" on the running back and the coach said he didn't believe it was a high ankle sprain.

On first-and-goal from the Jets 9 with just more than 2 minutes left in the half, Stewart took a handoff from Cam Newton and went down the right sideline for 7 yards before he was knocked out of bounds on a hard hit by LaRon Landry. Stewart stayed down for a few moments before being helped to the bench.

After trainers looked at Stewart's right leg, the running back was carted to the locker room -- but was smiling at his teammates as he headed into the tunnel.

Stewart signed a five-year extension worth $36.5 million, including $22.5 million guaranteed, earlier this month.

A first-round pick in 2008, Stewart is the second leading rusher in franchise history with 3,500 yards. He also holds the club record for single-game rushing yards with 206 against the New York Giants on Dec. 27, 2009.

Information from The Associated Press was used in this report.