49ers still have quality depth at running back

Posted by ESPN.com's Mike Sando

The 49ers have lost fullback Zak Keasey to a broken arm Friday night. Running back Thomas Clayton appeared to suffer a serious knee injury.

Losing Keasey could affect depth. Clayton was fighting longer odds in earning a roster spot, particularly after the team drafted Glen Coffee in the third round. Drafting Coffee even while Frank Gore was in his prime gave the 49ers quality depth at running back.

The 49ers kept only four running backs on their 53-man roster in Week 1 of the 2007 and 2008 seasons. Keasey's injury probably makes them less likely to open this season with five. Gore, Coffee, Michael Robinson and Moran Norris project as the likely four.

Robinson has the versatility to help at fullback if needed. The 49ers also like their one-back, two-tight end personnel group. The team should be OK as long as Norris, 31, stays healthy.