"I recall it happening in Sunday's game in the fourth inning," Posey said Thursday. "I can't remember what batter it was.
"They are going to take extra time to find out how I am. When they examined me (Wednesday) they felt I should have felt more normal after three days. When you are dealing with the brain, you've got to be cautious."
It's Posey's second time on the concussion list. He missed seven games because of a concussion in 2017. Manager Bruce Bochy said the team is being more vigilant because Posey has suffered multiple concussions in his career.
"You look at the history of the player and if there is more than one, you always have a little concern," Bochy said. "Buster wants to stay on top of this and avoid the risk of making this thing worse. Hopefully, that's what it is -- seven days."
The Giants also announced Thursday that pitcher Drew Pomeranz went on the 10-day injured list with a strained shoulder.
Pomeranz left his start against Cincinnati on Monday after allowing seven runs and nine hits in 1 2/3 innings. Pomeranz lasted just four innings in his previous start and has only pitched into the sixth once this season.
He is 1-4 with a 5.93 ERA in seven starts this season.
"When you look at the guy's last two starts, it makes sense to give him a 10-day break," Bochy said.
The Giants recalled catcher Aramis Garcia and right-hander Tyler Beede from Triple-A Sacramento. Garcia was in the starting lineup against the Rockies on Thursday.