In an interview with NFL Network's Michael Robinson, Sherman said he "made a fantastic decision" to join the 49ers because of what he saw from Garoppolo at the end of last season:
"I wouldn't have signed with the team if I didn't believe in him. I watched his film. I watched how he moved down the stretch, I watched how poised he was. I had conversations with his teammates, I had conversations with the head coach about how they coach him, about how he approaches the game. And just seeing his demeanor and seeing how he interacts with his teammates, I think I made a fantastic decision [to join 49ers]. I'm excited to see him go out there."
Garoppolo signed a five-year extension with the 49ers in February. He went 5-0 in five starts, completing 67.4 percent of his passes with seven touchdowns and five interceptions.
After spending seven years with the Seattle Seahawks, Sherman will try to get their NFC West rivals back to the top of the division.
The three-time All-Pro's first order of business will be getting himself back into playing shape. He told ESPN's Josina Anderson on Thursday that he's started jogging on a field for the first time since rupturing his Achilles last November.
Sherman is expected to be a key player in San Francisco's secondary. That unit finished 22nd in passing yards allowed (3,764) and tied for 24th in touchdowns passes allowed (27) last season.