"They had good guys [pitching] out there, and they swung the bats better than we did," Giants manager Bruce Bochy said.
Giants starter Madison Bumgarner wasn't quite as dominant as he had been previously in August, having gone 3-1 with a 1.55 ERA in his first four starts this month. After Heyward's third-inning blast, Bumgarner departed with one out in the seventh after allowing Michael Bourn's RBI single that drove in Minor, who had reached by doubling to right. Bumgarner was charged with four runs on seven hits and four walks in 6 1/3 innings.
"I just got out of whack, mechanically and mentally both," Bumgarner said. "I never really got back to where I needed to be."
Bumgarner matched a season high with four walks in the game, marking just the second time this year he has allowed more than two free passes in a game. He had walked Minor and Martin Prado ahead of Heyward's home run.
"I felt pretty good the first couple innings, and then the wheels just fell off from there," Bumgarner said. "I was still able to battle through it and get some outs, but when you're not feeling confident in your stuff and not feeling like you can put the ball where you want to, that makes it hard, especially against a team like that."
Minor had been dominant for most of the day, with the Giants first getting on the board in the fifth after Hunter Pence scored from third on Brandon Belt's groundout. Pence had reached after getting hit by a pitch and then advanced to third on Joaquin Arias' double.
After Buster Posey reached on a single to open the bottom of the seventh, Minor got flyouts from Pence and Arias before departing after Belt's double sent Posey to third. Chad Durbin came on in relief for the Braves and allowed Blanco's double as the Giants narrowed the deficit to 4-3.
The Braves picked up two more insurance runs in the eighth when Jeremy Affeldt walked Bourn and Martin Prado after inheriting a bases-loaded jam from Clay Hensley, and Atlanta got another in the ninth when Reed Johnson's double off Eric Hacker drove in Freddie Freeman. After the game, the Giants optioned Hacker to Triple-A Fresno and said a corresponding move would be announced before Sunday's series finale.
Minor held the Giants to four hits in 6 2/3 innings in his first career start at AT&T Park, striking out five while walking none.
"He threw the ball well and he made all the pitches," Pablo Sandoval said, adding that Minor's changeup and secondary pitches were especially difficult. "He threw strikes, and when you have a guy like that, it's going to be tough. That's what happened today."
Heyward hit a home run for the second straight game and now has five home runs and 11 RBIs in nine career games at AT&T Park.
"The crowd always keeps you on your toes here," Heywward said. "It's a good environment to play in. They're out there every night. It's a good team. They've got good pitchers. You've got to go up there focusing during every at-bat."
The Giants still have won seven of their last nine games and will go for their third straight series win Sunday.
"You can't have success every day," Sandoval said. "You have to keep your mind in the game every day, and tomorrow's another game."