49ers to keep Nick Bosa from preseason games after ankle injury

SANTA CLARA - Nick Bosa’s debut in a 49ers uniform is on hold until the regular season, and uncertainty now looms whether the rookie defensive end will be healthy for the Sept. 8 opener at Tampa Bay.

“We’re hoping for Week 1. We think he has a good chance for it but can’t guarantee that,” coach Kyle Shanahan told KNBR 680-AM before Thursday’s practice.

Shanahan termed it a “serious” ankle injury that could have been worse, adding that the team’s initial reaction was of a potential season ender for Bosa.

“We’re going to be very prudent,” general manager John Lynch said earlier on KNBR. “The great thing I can tell you about Nick Bosa, is he’s been dominating practice out here on a daily basis.

“He’s a game-changing type player, everything we hoped and expected and we have to get him right for this season.”

Bosa definitely will miss the exhibition season after going down in Wednesday’s practice, according to Lynch, who stopped short of calling it a “full-blown” high-ankle sprain, which usually takes at least four to six weeks to recover.

The 49ers conducted follow-up tests Thursday and Bosa’s progress will be closely monitored leading into the next month.

“We had a big pileup and a very big man fall on his leg,” Shanahan said. “We’re very fortunate he was a good enough athlete that he got his leg out of there, because a lot of other people it would have been their knee. There’s nothing he could have done about it.”

“We want him right,” Lynch added. “We’re not going to put his health or our team’s (at risk) ... We’re going to do what’s in the best interest and trust the ?medical staff on that, and trust Nick.”

Drafted No. 2 overall out of Ohio State despite missing all but three games last year with a core-muscle injury, Bosa looked phenomenal as a pass rusher and run stopper in training camp.

Then came practice No. 10, and he exited early, as was the case in May when he hurt a hamstring the second day of organized team activities and missed the rest of the offseason workouts.

“We don’t feel he is injury prone,” Lynch said. “Yesterday he had a big human being fall on his leg while he was engaged with someone else. Some of those things, that’s football. You can’t prevent that.

“We’re thrilled with what we have in Nick Bosa. We’re going to get him right and he’ll be a great player for a long time in this league.”

Lynch noted that Wednesday’s practice got “sloppy” with players falling to the ground too often and getting “mentally tired” at this stage of camp.

Dee Ford, the 49ers’ other marquee addition to their pass rush, has missed the past week of practice because of knee tendinitis that acted up in the fourth practice of camp.

Other defensive ends ailing are Arik Armstead (calf), Ronald Blair (groin) and Jamell Garcia-Williams (concussion).

That injury wave prompted the 49ers to sign defensive lineman Jeremiah Valoaga. Wide receiver Chris Thompson got waived in a corresponding roster move.

The 49ers have not ruled anyone else on their active roster out of the exhibition season.

However, coach Kyle Shanahan opened training camp by declaring quarterback Jimmy Garoppolo and linebacker Kwon Alexander out of Saturday night’s exhibition opener against the Dallas Cowboys. Both players are coming off knee reconstruction, and both are practicing well in camp.

Other candidates likely out against the Cowboys: cornerbacks Jason Verrett (ankle) and K’Waun Williams (knee); defensive ends Ford, Arik Armstead (calf), Ronald Blair (groin) and Jamell Garcia-Williams (concusion), guard Joshua Garnett (finger), running backs Jerick McKinnon (knee) and Jeff Wilson (calf) and linebacker Malcolm Smith (hamstring).