LaRoche delivered a two-out, two-run single in the ninth inning and the Pirates beat the Atlanta Braves 3-1 Thursday to split the four-game series.
LaRoche said he was just trying to make contact when he leaned forward to slap a 3-2 pitch from Rafael Soriano (1-1) up the middle for the tiebreaking hit.
"I'd already said to myself in the dugout 'Stay short, up the middle,'" LaRoche said. "I was happy to get a decent pitch to hit and hit it up the middle. ... I was lucky. It could have been right at the shortstop."
The Pirates managed only two hits in eight innings against Vazquez before collecting three hits in the ninth off Soriano.
Vazquez matched his season high with 12 strikeouts and took over the NL lead with 105.
Andrew McCutchen led off the Pittsburgh ninth with a single, moved up on a sacrifice and took third on a groundout. Adam LaRoche was intentionally walked and advanced to second without a throw on ball three to his brother.
Andy LaRoche followed with his go-ahead hit.
"I love that situation," Andy LaRoche said. "I love it when the crowd goes crazy and you're able to silence them."
Delwyn Young, who hit a fifth-inning homer, added a single before Soriano ended the inning.
Braves manager Bobby Cox was ejected by first-base umpire Brian Knight in the bottom of the ninth for a call that Kelly Johnson was out at first. Cox was tossed after throwing his cap to the ground, and it was the second time he came out of the dugout to argue a call by Knight.
The ejection was the 68-year-old Cox's first of the season and the 144th of his career, extending his major league record. Hall of Fame manager John McGraw is second in ejections with 131.
Vazquez, who did not walk a batter for the second straight start, gave up the homer to Young and a second-inning single to Andy LaRoche.
Vazquez, who has a 3.31 ERA, has a loss and two no-decisions in his last three starts despite allowing a combined total of four runs.
"I don't see how we're losing these games when he's starting them but we are," Cox said.
"You can't pitch any better than that. You just can't. He did everything right."
When asked if he could pitch any better, Vazquez said "Yeah. Don't give up the homer."
The Braves were 4-5 in a nine-game homestand and scored only five runs in the five losses, including back-to-back shutout losses to Milwaukee.
"There's only so many times you want to give the other team credit," Braves catcher David Ross said. "We just can't keep letting good pitching performances go by the wayside."
Atlanta acquired center fielder Nate McLouth at the start of the homestand in an attempt to spark the offense and called up first baseman Barbaro Canizares before Thursday's game. Canizares, who hit cleanup, was 1 for 4.
"I'm tired of being frustrated," said Chipper Jones, who did not have a hit. "We've certainly pitched well enough to be leading this division right now."
Paul Maholm gave up four hits and one unearned run in seven innings. He set a season high with eight strikeouts and walked three in his sixth no-decision in his last eight starts.
"I was kind of running out of gas," said Maholm. "I felt I had to go out every inning and put up a zero."
The Pirates pulled even in the fifth on Young's first homer of the season, ending their streak of eight straight games without a home run.
- Canizares was called up from Triple-A Gwinnett when INF Greg Norton was placed on the 15-day disabled list with a strained right ankle.
- Pirates RHP Charlie Morton, who lasted only one inning against the Braves on Wednesday night before leaving with tightness in his right hamstring, said he still felt minor discomfort on Thursday. He hopes to make his scheduled start on Tuesday at Minnesota.
- Diaz had two steals. His only other game with two stolen bases came on May 24, 2006, at San Diego. He is the first Braves player with two steals in a game this season.