Renteria singled to right with one out in the eighth inning. Schierholtz followed with a line drive to left field that Wladimir Balentien tried to grab with a diving catch. He missed, and the ball rolled to the wall for Schierholtz's second double of the game, allowing Renteria to score easily and give San Francisco its third consecutive win and fourth in its last five games.
"I was trying to put the ball in play with two strikes," Schierholtz said. "I thought it might have a chance to be caught. I watched it a little bit, then saw it got through."
One run was all San Francisco needed against the National League's worst-hitting team, which put just three runners on base while losing its fifth straight game and sixth in its last seven. The Reds, who had just one player from their Opening Day starting lineup in the lineup by the bottom of the first inning, went into the game last in the league in hitting and scoring.
First baseman Joey Votto left the game after the top of the first with blurred vision, leaving second baseman Brandon Phillips as the lone holdover from the Opening Day lineup. Five players who either opened the season with Triple-A Louisville or weren't in the organization at all were playing after Votto left the game.
"We've had a tough time scoring runs," Reds starting pitcher Bronson Arroyo. "It's tough without the guys you were going to depend on. Losing is old, whatever way you get there. That's about it. We haven't put up a lot of runs."
Schierholtz's hit snapped Arroyo's streak of consecutive scoreless innings at 17. Arroyo (11-12), who pitched a two-hitter in Cincinnati's 7-0 win over Washington last Thursday, allowed nine hits in eight innings.
Barry Zito and three relievers combined on a two-hitter. Zito gave up two hits over the first six innings. Relief pitcher Sergio Romo (4-2) struck out the side in the seventh inning and pitched a perfect 1 2/3 innings for the win. Jeremy Affeldt struck out Laynce Nix to end the eighth inning, and Brian Wilson pitched the ninth for his 30th save.
"Zito pitched great," Schierholtz said. "Our bullpen pitched great. I think Zito's ERA (4.26) is better than his record (8-11)."
The win allowed San Francisco to keep pace with Colorado in the National League wild-card race.
The Giants' win was just their fifth in 19 one-run games on the road.
Zito had a no-hitter and had allowed just one baserunner -- a Jonny Gomes walk with one out in the second inning -- before Adam Rosales blooped a single behind first base into short right field with two outs in the fifth.
Drew Stubbs had a double for the Reds only other hit, leaving manager Dusty Baker without answers.
"Things are piling up," he said. "Guys are doing the best they can."
The Giants had at least one hit in each of the first four innings against Arroyo, but they got just one runner past second base and hit into two double plays.
San Francisco got runners to second and third with two outs in the seventh inning. With his best pinch-hitter already in the game -- Schierholtz leads the Giants with 13 pinch hits -- Giants manager Bruce Bochy sent Fred Lewis up to pinch-hit for Zito. Lewis popped out to Phillips, leaving Zito with a no-decision in which he allowed just two hits and had four strikeouts.
"When we got runners on second and third, we had to go for it," Bochy said. "Lewis has been good coming off the bench. We had a hot pinch-hitter. The way our bullpen has pitched made the decision easier."
The start of the game was delayed 40 minutes by rain. ... The 1-0 score was the sixth in 547 games played at Great American Ball Park. ... The Reds placed CF Willy Taveras on the 15-day disabled list with a strained right quadriceps and called up Stubbs, who started as Cincinnati's leadoff hitter and in center field. Stubbs flied out to left field in his major league debut before doubling inthe sixth for his first major league hit.