Linebacker NaVorro Bowman’s comeback from an Achilles tear is progressing as a best-case scenario, and the 49ers are banking on the same to happen with first-round draft pick Reuben Foster’s right shoulder.

But what if Foster indeed needs a follow-up procedure on his rotator cuff because his initial one “didn’t take,” as some teams diagnosed before the draft, as ESPN reported Wednesday?

“The worst-case scenario is if the shoulder doesn’t heal correctly and you have to do it again,” Shanahan said Thursday on KNBR 680-AM. “When you have to do it again, you have to get another surgery and it’d be tough to play this year. You’d end up having him the next year but it’s not something that would hurt him long term.

“The worst case scenario is he wouldn’t be able to play for us right away,” Shanahan added, “but I still don’t think that would have changed how I personally would felt taking a guy with the 31st pick with the caliber of player we took.”

The 49ers moved up to draft Foster, the Butkus Award winner last season an Alabama, after receiving the advice of the team’s medical staff.

“They looked into everything with Reuben, and our doctors felt good about his shoulder,” Shanahan said. “They thought it was recovering well. They didn’t have the same report a lot of other teams did.

“You never know who’s going to end up being right. Everybody is doing their best to figure it out. No one can tell the future.”

Foster, at his introductory press conference Friday, disputed the notion he’ll need more surgery. He predicted he’d be limited in the offseason program into June but that he’ll be “full go” come training camp in late July.

If healthy, Foster should form a dynamic duo at inside linebacker with Bowman, who tore his left Achilles on Oct. 2.

“I couldn’t be more excited with Bo than I am right now,” Shanahan said Thursday. “He’s been winning our drills, our shuttles. To come out there and watch him, he does not look like a guy coming off an Achilles (tear). I thought it would take him some time. I did not think he’d be looking himself until training camp.”