"Not sure of the severity, whether it was low or high," head coach Kyle Shanahan said of the injury.
Reid was limited to just 10 games last season while dealing with a torn biceps.
A first-round pick in 2013, Reid made the Pro Bowl as a rookie after tallying 91 tackles and four interceptions. However, he has seemingly made a smaller impact each season since, only grabbing one interception in the last two years combined.
The 25-year-old is heading into his last season under his current contract, and he is switching positions in the process under a new defensive scheme from free safety to strong safety.
"I feel like I was made for this position with my body type being a bigger safety, so I’m excited about this year," Reid said, per Nick Wagoner of ESPN.com. "[Hitting is] my favorite part of the game. I used to get mad at myself if I didn’t have at least one big shot, so to have that type of mentality for everybody, I tell the guys all the time I don’t do a lot of talking; I let my pads do the talking."
Jimmie Ward and Jaquiski Tartt will likely take over the safety roles while Reid is unavailable.