BRADENTON, Fla. -- Led off by starter Clay Buchholz's three hitless innings, five Boston pitchers combined on a four-hitter Sunday as the Red Sox downed the Pirates, 4-1, at McKechnie Field.

Buchholz, who had allowed a run on three hits in his only other outing of the spring, issued a leadoff walk in the third inning to Jordy Mercer for Pittsburgh's only baserunner until the Pirates broke through for three hits in the seventh.

Gregory Polanco led off with a single to deep short off Rubby de la Rosa and was erased on a force-play grounder by Chase d'Arnaud, who stole second before scoring on Chris McGuiness' single.

Charlie Morton, unscored upon in five innings in his first two starts, fell behind 2-0 on a two-run single by Jackie Bradley Jr. in the second and Mike Carp added a solo homer off him in the third. Carp has two homers and three RBIs this spring -- all in two games against the Pirates, who have reportedly been scouting him in the event they decide to add a veteran lefty-hitting first baseman.

"Sinker," Morton said of the pitch he threw Carp. "I worked him in on his first at-bat [when Carp squibbed a single to the third-base bag], and I stayed in and he was sitting on it. And I missed; the ball really didn't do anything. Pure swing, pure contact."

Jason Grilli and Mark Melancon, the back end of the Pirates' bullpen, each worked a perfect inning with two strikeouts.

Up next: Right-hander Jay Jackson, hoping to turn a chance into a job challenge, makes his second spring start as the Pirates host the Orioles at 1:05 p.m. ET at McKechnie Field. Jackson blanked Toronto on one hit for two innings on Wednesday, when he stepped in as Jeff Locke was scratched with a sore right side. A six-year Minor Leaguer with 103 Triple-A games, Jackson has four shutout innings overall in Grapefruit League play.