Not so fast, said offensive coordinator Jimmy Raye.
Rookie Anthony Dixon made an impressive NFL debut in Sunday's preseason opener against the Indianapolis Colts, and that will keep him in the mix for more playing time despite a so-so postgame review from head coach Mike Singletary.
"I think Anthony Dixon is very much in the running for time at that position as the guy that goes in and replaces Gore," Raye said after Wednesday morning's practice. "I think he put himself in position to warrant more snaps against better competition."
That means Dixon will probably see ample time in the 49ers' backfield Sunday night against the Minnesota Vikings. Westbrook, who took his first snaps since signing on Monday, also might play, but that's still to be determined.
Raye said Westbrook will first need clearance from the training staff to play. Then the team will have to decide how much to use him.
"What we don't want to do is put him out there and he's not sure what he's doing," he added. "He hasn't been in training camp or in the offseason program, so we don't want to create a situation physically that we could avoid if we're patient and take our time. That'll be determined as we get further along in the week."
Raye wouldn't talk about how he intends to use Westbrook, although the prospect of two pass-catching running backs in a game at the same time sounds intriguing. But working him into the game is not something he wanted to discuss.
"If I tell you that, I might as well tell the whole league," he said. "We'll determine that as we go."
What's clear, however, is that Dixon hasn't been shoved into the background with the addition of Westbrook. Although Singletary said Dixon played "OK" on Sunday, Raye indicated there was a lot to like in the rookie's 100-yard rushing day. He also had three catches for 22 yards.
"The physicality with which he ran the football, his ability in the backfield to take a minus-five yard play and turn it into a 19-yard play," he said. "His ability to play without the ball was something we had concerns about, but all in all, the performance of a first-year guy in his first opportunity was pretty good."
With the Niners preferring to limit Gore' workload in the preseason and hold back Westbrook until they're sure he's healthy and knows learns more of the playbook, it's an opportunity for Dixon to impress his coaches.
"I just wanted to go out and push the envelope a little bit," Smith said. "I sped up a little bit in there. I got the ball out really early and it was a matter of being 18 inches, two feet off. That's the difference between a touchdown and an incompletion. It's something we've hit all camp, but you've obviously got to do it in a game."
He reiterated his postgame comments that he felt good in the game, although he added, "That's probably as good as you can feel with a QB rating of 7.0."
SITTING OUT: Tight end Vernon Davis (knee) and wide receiver Michael Crabtree (neck) did not take part in practice, although Davis got some work in on the stationary bike and Crabtree did some light work on the side. Ray conceded that their absence slows the work the team needs to do on offense.
"It's always a constant changing deal for the quarterback," he said. "At some point, the unit needs to be together and practice together, and that's been a hit or miss with the injuries. You expect that in training camp, but for us it's gone on a little longer than usual. Whenever they're healthy and ready to go, we'll try to pick up and go double-time."
Kicker Joe Nedney took his first kicks since training camp began, saying afterward that a persistent groin injury he's endured most of his career has forced him to take things slowly.
"It's something I've learned to deal with my entire career," he said. "When you're 37 instead of 23, you've got to deal with it in different ways."