"Rookie Kendall Hunter continues to make a case that he should be Frank Gore's primary backup this season.

Hunter entered Thursday's game as the NFL's top rusher in the exhibition season and immediately started to pad his lead. He carried the ball six times for 46 yards on the opening drive, including a 21-yard scamper on third and short. He finished with 57 yards in the 20-17 win over San Diego.

Gore started the game at tailback but left before getting a carry.

While Anthony Dixon had gotten into the game ahead of Hunter in the three previous preseason outings, Hunter took the first carry against the Chargers.

"He's definitely playing well enough to be the No. 2 back," coach Jim Harbaugh said.

Dixon ran only once on the first drive – for a one-yard touchdown. Dixon scored again from one yard out at the end of the first quarter.

A 49ers tailback has led the exhibition season in rushing in three of the last four seasons. Dixon did it a year ago. He finished with 13 carries for 45 yards Thursday."