"Though Brian Westbrook could make his 49ers regular-season debut Sunday, it's unlikely the running back will have anything more than a cameo.

Westbrook insisted he is healthy -- "about 100 percent," he said Thursday -- but offensive coordinator Jimmy Raye sounded reluctant to press his luck when it comes to the running back's balky hamstring.

"My biggest concern with a player that doesn't go through the offseason program and training camp is that you run the risk of a setback from a strain or a pull, and that's what happened to him," Raye said.

The two-time Pro Bowl running back signed with the 49ers on Aug. 16 and had only two carries during exhibition play before sustaining what the team called a "hamstring cramp" Aug. 28.

He has been limited in practice since. Eventually, the 49ers envision him as dual-threat out of the backfield with Frank Gore.

But, Raye said, not "until he gets ground into shape, football-shape, and he's feeling good physically about himself."

Westbrook sounded as if he was feeling fine Thursday. He ranks third in the NFL since 2004 with 8,561 scrimmage yards and leads all running backs with 380 catches and 25 receiving touchdowns during that span.

"I think I'm ready to play," Westbrook said. "I mean, Jimmy's the coach, so it's his decision as far as who plays and how much, so whatever he says goes, but I'm ready to play.""