He received a no-decision in his only other matchup with San Francisco, a 10-8 Brewers win April 16 at Miller Park.
Jim Henderson pitched the ninth for his 16th save in 19 chances.
Posey, last season's NL MVP and batting champion, was hit by a pitch from Peralta above his left elbow with two out in the sixth, and Posey grimaced in pain as he slowly walked to first.
"It's frustrating. All of us take a lot of pride to be in those situations and come through," Posey said.
Bochy is considering trying Hunter Pence in the leadoff spot — perhaps now as soon as Wednesday night. While he had previously planned to rest Marco Scutaro in Thursday afternoon's finale, Scutaro will now get a break Wednesday after he went hitless in four at-bats Tuesday and is 0 for 9 overall in the leadoff spot the past two games.
"He needs a break," Bochy said.
Right-hander Marco Estrada returns to the mound for the Brewers on Wednesday night for his first start since June 3 after spending time on the disabled list with a left hamstring strain.
NOTES: Bochy said CF Angel Pagan is progressing well in Arizona from left hamstring surgery and could return to the Giants as soon as Sept. 1. ... San Francisco assistant GM Bobby Evans said the club is yet to sign LHP Ted Lilly to a minor league deal. He was designated for assignment July 25 by the Dodgers. "Upon reviewing Ted Lilly's medical history we're going to hold off on pursuing a minor league contract right now," Evans said. ... Giants LHP Barry Zito received the Lou Gehrig Memorial Award given annually by the Phi Delta Theta International fraternity to an MLB player. Zito started Strikeouts for Troops nine years ago to help returning veterans and their families with medical and other bills. "It's a huge honor," Zito said. "Lou Gehrig's name obviously is one that brings to mind a special feeling for most people."