Head coach Kyle Shanahan got into work before 6 a.m. on Friday morning and walked by the weight room to see his starting left tackle, Joe Staley, trying to get himself prepared to practice for the first time this week. There is still a chance that Staley plays on Sunday against the Arizona Cardinals after sustaining a knee injury during the 49ers' Week 4 loss to the Los Angeles Chargers.

If Staley can't go, Garry Gilliam will replace him in the starting lineup on Sunday, said Shanahan during a Friday-morning KNBR interview.

On the other side of the offensive line, right tackle Mike McGlinchey is also nursing a knee injury. He, however, was able to return to practice on Thursday and expects to play on Sunday. Shon Coleman, whom the team traded for on August 31, would replace McGlinchey if both starting tackles sat out this weekend.

That's not the only injury news along the offensive line. Center Weston Richburg is also dealing with a knee injury. He too missed Wednesday's practice and, like McGlinchey, was limited on Thursday.

"You've got to give the guys a chance to get healthy enough to try to practice," Shanahan said on the "Murph & Mac" show. "They'll definitely be better on Sunday than they will today, but it's very hard just to find out on Sunday because you have to decide a few hours before the game who's active.

"Then you activate them, and they go out two plays, and they realize they can't go. Now you've got to play a whole game without an O-lineman. You've got to put a tight end in there or something, and that can be pretty catastrophic.

"You try to get them healthy enough to where they can practice at least one day. Today's our last day to do that, so hopefully, they can go out there, show that they'll be able to do it and be good enough two days from now. If that's the case, I know it will help a lot."

Friday's practice will be significant for evaluating wide receiver Marquise Goodwin's health. He is dealing with a hamstring and quadricep injury. Shanahan says that if he appears to be running at about 90 percent on Friday, then he should be good to go. If that's not the case, Richie James will get the call.

"As you guy saw Richie in the preseason, he can make some plays," Shanahan said. "I feel good with going with him if it doesn't work with [Marquise]."

Shanahan expects to have both safeties, Adrian Colbert and Jaquiski Tartt, back for Sunday's game. The goal is to consistently have Colbert, Tartt, and linebackers Reuben Foster and Fred Warner in the middle of the defense.

"If we can get those four guys in there for a consistent amount of games, it will give us a chance to build some continuity and get better," Shanahan explained.

Shanahan didn't expect cornerback Richard Sherman to be available this week after the cornerback suffered a calf injury just under two weeks ago. Sherman also returned to practice on Thursday.

"He's a different bird," Shanahan said. "He got out there yesterday, said he could go. We watched him. He did a decent job yesterday. We only let him go through a little bit of practice just to see. That's more than some of these other guys have been doing that I mentioned so today will be a big day for Richard. We'll watch him hard, talk to him about it, and if he does good, feels like he can get through this game healthy, he'll go."

Shanahan said he wants to be sure Sherman is healthy enough to play because he doesn't want to risk further injury to one of his best defenders.

You can listen to the entire conversation with Shanahan below.