SANTA CLARA -- Wide receivers Michael Crabtree and Brandon Lloyd are expected to miss the next week or two because of injuries that are unspecified but believed to be leg related.
"Maybe a week, maybe two weeks," Harbaugh said Friday of Crabtree's status, "and same with Brandon Lloyd."
Crabtree, who did not practice Thursday, is battling a sore hamstring, according to ESPN's Josina Anderson. Harbaugh would only say that Crabtree's injury is not related to his surgically repaired right Achilles or previously fractured feet.
"He's got something he's working through and we're going to get it 100 percent," Harbaugh added.
Lloyd, coming off a year hiatus, did not finish Wednesday's practice, as was the case with Crabtree, who's otherwise looked stellar through camp.
Harbaugh shed light on several other health situations:
-- Tight end Vernon Davis was held out of team drills Thursday as a precaution because he wasn't loosening up to Harbaugh's standard.
-- Running back Marcus Lattimore (knee) remains on the non-football-injury list because he's still not 100 percent, Harbaugh reiterated in a camp-long theme.
"There's a percentage that needs to get better," Harbaugh said. "He's working very hard toward that and we're going to do what's best for him.
"Marcus is going to be part of this team in some form or fashion. I know what he has inside him and what he's capable of doing on the football field. We'll continue to do what's best for him and ultimately what's best for the program."
-- Center Marcus Martin (ankle) participated in individual drills and could be joining full practice soon, as is the case with linebacker Aaron Lynch, Harbaugh said. Martin's delayed start has impacted his competition for the starting job with Daniel Kilgore, to an extent.
"He's put in a lot of good work in the time since he was drafted (in the second round), with the OTAs and minicamps," Harbaugh said of Martin. "He's been outstanding in the meetings. I sat in on a meeting yesterday where he was making calls and understanding things. It's a later start than he would have liked but he'll be back in there soon."
-- Tight end Garrett Celek has a disk issue in his back and the 49ers are in a wait-and-see mode while he's on the physically unable to perform list.