Two innings later, Posey and the Giants got a break.
Posey hit a two-out single to the same spot Parra robbed him earlier and Nate Schierholtz followed with a two-run triple, helping San Francisco stay close to the NL West lead with a 2-0 win over the Arizona Diamondbacks on Monday.
"Off the bat, I thought it was going to be down," Posey said of the first ball he hit at Parra. "You kind of know when they're going to fall and he came out of nowhere to make a great catch."
Madison Bumgarner matched zeros with Arizona starter Ian Kennedy into the eighth inning and three Giants relievers combined to escape a jam after he left. Parra preserved the scoreless tie with his diving catch in the ninth, but San Francisco's Santiago Casilla (6-2) struck out the side in the 10th.
Aubrey Huff got the winning rally started with a two-out single off Aaron Heilman (5-7) in the 11th, then Posey followed with his dink single in front of Parra, whose dive came up just short this time. Schierholtz put San Francisco ahead with his triple to the right-center gap and Brian Wilson matched a career high with his 41st save in the bottom half, giving the Giants their sixth victory in eight games.
San Francisco remained one game behind first-place San Diego, which ended a 10-game losing streak with a 4-2 win over the Los Angeles Dodgers.
"It's fun, especially since we're back in it now," Bumgarner said. "It's fun to come out here every day and everybody's excited to get to the park and compete."
Not everyone was able to enjoy it on a day hard liners and even bats seemed to be flying into the stands on nearly every at-bat.
The worst of it came when two kids were injured on consecutive at-bats in the fourth inning.
A 13-year-old boy, who was sitting just beyond the protective netting on the third-base side, was injured when Posey lost his bat swinging through a pitch by Kennedy. The boy was struck on the right side of the head and was carried off on a stretcher to a hospital.
Medical workers were still attending to him when Pablo Sandoval set a foul ball into the upper deck that struck a 2-year-old girl on the forehead. She also was taken to the hospital.
"Anytime that happens it is scary," Posey said. "Balls were flying in the dugout, bats in the stands, you have to be on your toes. I hope they're all right."
On the field, nobody could get to Kennedy or Bumgarner.
Kennedy was sharp for the fifth straight start, striking out six and retiring 14 of his final 15 batters.
The right-hander did a little work with his bat, too, leading off the eighth with his first career double. He was stranded at third after Javier Lopez struck out Kelly Johnson, and Ramon Ramirez got Chris Young on a fielder's choice to end the inning.
"I feel good right now. I was throwing a lot of strikes today," Kennedy said. "I didn't have a whole lot of strikeouts. I put the ball in play and let my defense do the work."
Bumgarner matched Kennedy almost pitch for pitch.
The left-hander struck out seven and twice got Adam LaRoche with two on and two outs: on a strikeout in the first inning and a fly ball to the warning track in right in the sixth. Bumgarner is 1-0 with a 1.13 ERA in three career starts against the Diamondbacks, but has just one win over his last eight starts this season.
"Everything was working for the most part today," Bumgarner said. "I didn't throw the cutter a lot, but the fastball velocity was good. Everything felt good."
Heilman felt good, too, but it didn't work out as well.
The former closer took the loss Saturday against Houston after Carlos Lee hit a three-run homer off him and made it two defeats in three days by giving up two soft singles and Schierholtz's hard-hit triple.
"I left one pitch up and it hurt me," Heilman said. "You are always one pitch from getting out of the inning and one pitch away from getting yourself in trouble. You go out there and try to make pitches the best you can, but unfortunately sometimes they don't go the way you want them to."
Giants SS Juan Uribe didn't play after fouling a pitch off his left shin Sunday against the Dodgers. ... Arizona RF B.J. Upton missed his fifth straight game with a strained left shoulder. ... The Giants have won five straight road games.