San Francisco 49ers guard Joshua Garnett has missed the team's last five practices after banging his knee against a teammate during a practice on July 28. Head coach Kyle Shanahan was surprised he did not practice on Wednesday. Then Garnett missed Thursday and Friday's practices.

What was initially assumed to be a minor injury may be a bit more serious, according to Shanahan. Without getting into specifics about the injury, the 49ers head coach told reporters on Friday that Garnett was getting a second opinion. That second opinion appears to have provided some good news, according to Tom Pelissero of NFL Network.

There is some concern because the injury occurred to the same knee that kept him out all of last season. While he won't need surgery, it is unknown how long Garnett will continue to miss practice time. He continues to be listed as day-to-day on team-provided injury reports.

"There is concern," Shanahan said. "Josh said that he doesn't feel right and that's always worrisome when a player doesn't feel right. Josh is getting a few second opinions. We'll wait until our doctors talk to a few other people and we'll see what conclusion they come to."

Garnett is supposed to be fighting for the starting right guard job and possibly even a roster spot. With Jonathan Cooper returning to practice soon and Mike Person and Erik Magnuson taking advantage of the extra reps, the general belief is that Garnett's future with the 49ers might be in jeopardy if he continues to miss time.

"Josh went through a lot last year with his knee and took his season off treating it right," Shanahan said. "He got himself ready to play, came in here, had good OTAs, had a couple of good practices, then he hit his knee, and it's worried him. I understand that. But he doesn't feel right, and we're trying to figure out what it is and, hopefully, we will."

Garnett is one of just 13 players from the 2016 roster who remains on the team.

Cornerback Richard Sherman left Friday's practice with a tight hamstring, according to Shanahan. The injury is not believed to be a serious one.

"I didn't see him fall, but they told me out there his hammy got tight on him," Shanahan said. "They took him out, and we'll see after I talk to [head athletic trainer Jeff Ferguson]."

49ers players have Saturday off and resume practice on Sunday morning.