"It's nothing crazy," Posey said. "It's just off a little bit."
He said he felt "pretty back to normal" between the time his previous episode subsided and Thursday.
Posey, who's in a 3-for-34 skid that has lowered his batting average to .254, declared himself available to pinch-hit.
Giants manager Bruce Bochy indicated that he didn't consider Posey's injury serious and rejected the notion that this could be a recurring health issue. But Bochy wants to guarantee that Posey's ailment doesn't become chronic.
"We'd like to get this thing taken care of," Bochy said.
Hector Sanchez replaced Posey, starting his 18th game behind the plate.
Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. This story was not subject to the approval of Major League Baseball or its clubs.