BOSTON – After 7 1/2 innings of strong pitching and just enough big hits to build a two-run lead against the Red Sox, the Braves melted down. Again.

This time it was fielding blunders, including a costly error apiece against each of the Upton brothers in the Braves outfield, that served as the accelerant in a four-single, two-run eighth inning that tied the score for the Red Sox, who pulled out a 4-3 win against closer Craig Kimbrel on a walk-off hit and error in the ninth.

Kimbrel, who got the last out of the sloppy eighth inning, walked the first two batters in the ninth inning before Xander Bogaerts hit an infield single to Chris Johnson, whose throw to second base was dropped by second baseman Tommy La Stella, allowing Jackie Bradley Jr. to score the winning run.

It was the second major league game for La Stella, who was called up from Triple-A on Wednesday.

The last two innings was ugly, agonizing stuff for the Braves and their fans, who’ve watched the team squander leads and fail to to take advantage of opportunities the way the Red Sox did again and again while sweeping four straight games in the home-and-home series with the Braves. This after the Red Sox lost 10 in a row before coming to Atlanta Monday.

Mike Minor pitched seven strong innings and the Braves led 3-1 until the eighth inning, when Brock Holt led off with a single against reliever David Carpenter and left fielder Justin Upton booted it to allow the runner to reach second. Bogaerts followed with a single that was enough to score Holt from second to cut the lead to 3-2.

Dustin Pedroia hit what was ruled the third consecutive single of the inning, a possible double-play grounder that La Stella tried to field behind second base and fell as he did so. A.J. Pierzynski added another single to center field, where B.J. Upton had it glance off his glove for another error, allowing the tying run to score and Pedroia to advance to third.

The Braves escaped without further damage after Carpenter struck out Jonny Gomes, left-hander Luis Avilan struck out Grady Sizemore and intentionally walked David Ortiz, and Kimbrel got David Ross to fly out to end the inning with bases loaded.

It was the first time this season that Kimbrel entered a game in the eighth inning, when he came back out for the ninth he walked No. 9 hitter Bradley and Holt consecutively to start the inning.

Jason Heyward’s two-out solo homer in the third inning gave the Braves a lead would hold until the eighth, as Minor showed how far he’s come since the last time he faced the Red Sox at their venerable ballpark.

Minor allowed seven hits and one run in seven innings and was in position to get his third time in four quality starts since getting knocked around by the Cardinals three weeks ago. That is, until things fell apart after he left the game.

The Braves blew leads in three of the four losses including a lead after the sixth inning in two games.

Minor had three strikeouts and no walks and retired seven of the last eight batters he faced after Brock Holt’s two-out double off the left-field wall in the fifth inning cut the Braves’ lead to 2-1. The Braves added an insurance run in the eighth when B.J. Upton hit a leadoff single and scored on Freeman’s long double to center field.

But it wasn’t enough insurance for the gaffes that ensued in the eighth.

In his only previous start against the Red Sox, Minor allowed seven runs (four earned) and three homers in 4 2/3 innings of a loss on June 24, 2012. That left him with a 3-6 record and 6.14 ERA through 14 starts that season, and worried that he might soon get sent to Triple-A.

But he stayed in the majors and soon figured some things out. Minor gave up four runs in five innings of a win against Washington six days later, and in 53 starts since he’s 22-16 with a 2.95 ERA. He began this season on the disabled list, gave up 11 hits and six runs in 4-1/3 innings against the Cardinals in his second start, but in four starts since Minor is 2-1 with a 2.02 ERA.

He was staked to a 1-0 in the third inning on Heyward’s two-out home run, his fifth of the season and second in three nights against the Red Sox. The Braves’ imposing leadoff hitter has three homers among six extra-base hits in seven career games against Boston, including two homers in five games at Fenway Park.

Heyward has hit .318 (21-for-66) with three homers and an on-base percentage above .400 in his past 17 games. He went 1-for-5 and struck out with a runner at second base to end the eighth inning.

The Braves extended the lead to 2-0 in the fourth inning when Freeman drew a leadoff walk, advanced to second on umpire Bob Davidson’s balk call against Jake Peavy, and scored on Evan Gattis’ one-out single to the left-field corner. (They don’t call Davidson “Balking Bob” without reason, as ex-Braves star Chipper Jones noted on more than one occasion.)