Posey, batting with a runner at third and two outs in the bottom of the first, couldn't avoid the pitch from Arizona's Taijuan Walker, which hit him near the crown of his helmet.
He immediately went down, with manager Bruce Bochy and trainer Dave Groeschner racing to the plate.
Posey stood on his own, but Bochy pulled him from the game so he could be monitored by team medical staff.
"He's fine," Bochy said after the game. "It's a scary moment, a dangerous moment. But that doesn't mean there's something there."
Both teams were at pains to say there would be no lingering ill feeling from the incident when they play again on Tuesday.
Walker said the pitch that hit Posey just got away from him.
"I never want to do that," Walker said. "I have before. It's scary. It's something I never want to do. That one just got away from me."
But Moore insisted it wasn't intentional payback.
"Leading off the eighth inning, we have a three-run lead?" Moore said. "No way."