SANTA CLARA – Linebacker Reuben Foster entered his rookie season with a lot of expectations and more than a few concerns.

While he has been a productive player whenever he’s been on the field, Foster missed six games due to injuries -- a high-ankle sprain and bruised ribs. But none of his time missed has been connected to right shoulder surgery he underwent before the draft.

Four other times, Foster has required medical attention on the field, only to return to action without missing any significant playing time.

“I mean the guy just wants to kill people,” 49ers defensive coordinator Robert Saleh said on Thursday. “So sometimes he kills himself for a play.

“He hits the daylights out of people. Every once in a while, he’s going to get something where he might have to take a breather. It’s been a while since I’ve seen someone who hits as hard as he does. I think after a full offseason where he can just build his body instead of having to rehab, eat right and do things the right way, I think he’ll avoid some of those injuries as he gets smarter in the game.”

Foster had the wind knocked out of him two weeks ago when Houston Texans running back Lamar Miller hit him in the midsection as he was blitzing. Last week, Foster missed two snaps of defense due to a neck stinger.