The Pirates scored four times in the eighth.
Pedro Alvarez hit a tiebreaking two-run shot off Anthony Carter for his first home run of the spring.
Buchholz allowed four hits, struck out four and walked one in 5 1-3 innings.
Garrett Jones hit his first spring homer leading off the second for Pittsburgh's only run against the right-hander, who went 11-8 in 29 starts last year.
Jeff Locke, competing for a spot in the Pirates' rotation, gave up three runs, two earned, and seven hits in four innings.
Jarrod Saltalamacchia had two hits and drove in a run for the Red Sox.
Braves (ss) 10, Blue Jays 5
DUNEDIN, Fla. (AP) --
Brandon Morrow allowed four of his five runs in the fifth inning Saturday of the Toronto Blue Jays' 10-5 loss to an Atlanta Braves' spilt squad.
Morrow gave up eight hits in 5 1-3 innings and has allowed 15 runs over 15 innings in five starts.
Reed Johnson had a two-run single, the Braves' fourth consecutive hit off Morrow with two outs in the fifth, that pulled Atlanta to 4-3. The tying run scored on Morrow's wild pitch, and Justin Upton's run-scoring infield single put Atlanta ahead.
Minor league callup Edward Salcedo hit an eighth-inning solo homer and had a three-run drive in the ninth for the Braves.
Rajai Davis, Melky Cabrera and J.P. Arencibia hit solo homers off Sean Gilmartin, who gave up five runs and 10 hits in five innings.