The Giants announced Posey was removed to be watched for concussion symptoms.
Manager Bruce Bochy said Posey was feeling better after the game.
"He had the [concussion] test done. He got light-headed when he was on first base," Bochy said. "We will monitor him overnight. He will be off [Saturday], but if all goes well he could be in there Sunday."
Posey had to gather himself after the blow to his mask in the second inning. He singled in the third inning and, upon reaching first base, was tended to by a trainer and first base coach Jose Alguacil.
Posey took off his helmet and walked to the dugout. Nick Hundley came on as a pinch runner.
The Diamondbacks went on to win 6-3.
Information from The Associated Press was used in this report.