Athens — Georgia running back Kregg Lumpkin underwent surgery Tuesday to repair his broken right thumb and could be out up to four weeks, Bulldogs coach Mark Richt said.

Lumpkin broke the thumb in the third quarter of Saturday's season-opening win against Oklahoma State.

"I was running through the hole and got hit and tried to brace myself when I fell, and my thumb went into the ground at an angle," the senior said. "When I looked at it, it was leaning out of my glove."

Coaches hope to have Lumpkin back in 2-3 weeks and let him start playing on special teams. In 3-4 weeks, he might be able to start to grip the ball with his hand and could work his way back into the running back rotation, Richt said.

Lumpkin doesn't have a definite idea of when he will return.

"I've just gotta get healed up and bounce back," he said.

Lumpkin's injury leaves Georgia with Thomas Brown and Knowshon Moreno as the primary options at running back. That pair had 118 rushing yards against Oklahoma State. Senior Jason Johnson and redshirt freshman Shaun Chapas are fullbacks who could also play running back.

Georgia also has star recruit Caleb King but it's not likely coaches would burn King's redshirt season since Lumpkin won't miss the entire season.