Following Sunday night's exhibition contest against the Minnesota Vikings, Kyle Shanahan held a conference call on Monday and gave updates on injuries, position battles and finalizing the 53-man roster.

Take a look at the top four notes from the head coach.

1. A Collective Exhale

The 49ers were relieved to leave Minneapolis virtually unscathed despite Joe Staley's unspecified knee injury. Just six snaps into Sunday night's contest, Staley left the game early but appeared at ease on the 49ers sideline. Staley was diagnosed with tendonitis on Monday morning and will take Thursday night's contest off to recuperate. Shanahan is optimistic the vet will be ready to go by Week 1 of the regular season.

"You could tell he just caught it a little bit on the turf. I think it scared him more than anything," Shanahan said. "I know he wanted to fight through it and I'm sure he could have, but he landed a little awkwardly on it. We just wanted to be safe with him and we'll take it safe with him this whole week up to Carolina, make sure he's 100-percent when we start that game.

2. Last Call

Sunday night served as a trial run for the 49ers starters, seeing an increase in snaps from the first two games. Week 4 of the preseason is the final opportunity for rookies and "bubble" players to showcase themselves for a spot on the 49ers roster.

Some first-team players may still see playing time if Shanahan feels he needs to see more.

"We plan on sitting a number of guys. Not saying that's going to be all starters," Shanahan said. "There's certain people we need to see more on that we're trying to figure out who this 53 is. There's some guys we want to rest to just make sure they're healthy because they are a little banged up. I know for sure we're going to sit a number of people, most of the starters, but it's always hard to sit all of them."

3. The Ferrari is Ahead of the Curve

Reuben Foster has exceeded Shanahan's expectations. The injury to Malcolm Smith moved Foster up the depth chart earlier than expected, and so far, he is making a name for himself as an every-down player.

"He's come a long way. I think that's what's been real exciting about Reuben," Shanahan said. "Missing all of OTAs, not playing in a system this way in college, not being the MIKE linebacker down in and down out like he was in college, and really not being able to go through it in OTAs. I did have a lot of worries about it, knowing it would take some time. I think he's ahead of schedule. He's a very smart person. He works at it. He loves football. He gets a lot out of the meetings, gets even more obviously out of practice and games. He is further along than I anticipated in terms of the X's and O's part. I think (Sunday against the Minnesota Vikings) was the first time we all saw him really cut it loose."

Foster led the 49ers defense on Sunday with eight tackles in two quarters against the Vikings.

4. Running Back Conundrum

Shanahan has some difficult decisions to make over the few days. One of which is sorting out the surplus of talent at running back. Four of the six 49ers running backs received touches on Sunday. Undrafted rookie Matt Breida received snaps behind veteran Pierre Garçon. But before jumping to any conclusions, Shanahan has yet to make a final verdict on the 49ers running back group.

"We wanted to give him a chance. He's done a good job," Shanahan said of Breida. "We wanted to see him out there as little bit earlier in the game, especially against a good defense like Minnesota. I thought he did a good job. I thought the other guys did too. We've got some tough decisions here to make at running back, but we're going to let it all play out. We definitely need this game on Thursday to see the other guys too. They've all made it real tough on us."

That also includes veteran Tim Hightower who didn't play a single snap on Sunday. Shanahan said he already has a good feel for Hightower's ability, but the veteran will receive playing time on Thursday.

"We just had a bunch of guys that we haven't seen before and we've had to get some of these rookies more opportunities because you never know what you've got with them until you see them in NFL games," the head coach added.

The depth of the backfield will be interesting to monitor as the team works towards the final 53.