Belt was struck by a ball in the face while fielding during batting practice Saturday. Tests on Sunday confirmed the concussion, Manager Bruce Bochy said.
Belt was to fly with the Giants to Philadelphia, where they begin a four-game series Monday. He sat out 50 games because of a broken left thumb before returning July 5.
CC Sabathia talks about knee surgery
CC Sabathia is disappointed and relieved all at the same time.
Sidelined because of a right knee injury, the New York Yankees left-hander spoke to reporters Saturday morning for the first time since the team announced he will have season-ending surgery Wednesday.
Sabathia said the news was difficult to absorb and his situation is "not fun." But he's glad doctors recommended an arthroscopic cleanup rather than microfracture surgery, which would have required perhaps an 18-month recovery.
"It's tough. It's unfortunate," Sabathia said. "But I feel, I guess, relieved that I have some answers, and kind of a plan in place to kind of move forward."
Sabathia, who turns 34 Monday, said he's confident he will be back on the mound in spring training. And with a blueprint now in place for his return, he said he was able to get "some real sleep" Friday night for the first time in weeks.