Buchholz and Maholm each allowed one hit and one walk.
The game ended on an unusual triple play after Jonathan Van Every was hit by a pitch from Michael Bowden and Brandon Jones walked to lead off the ninth.
Gorkys Hernandez lined to shortstop Red Sox shortstop Jose Iglesias. Iglesias flipped the ball to second baseman Tug Hulett for the second out. Hulett threw to first and the ball got by Aaron Bates. Catcher Dusty Brown was backing up on the play, got the ball and threw to second to get Jones, trying to advance on the play.
Both Buchholz and Maholm were scheduled to pitch Friday, but heavy rains wiped out the Grapefruit League schedule, giving each pitcher an extra day of rest.
"I had that extra day and felt really good, might have felt too good with some of the pitches that I was trying to throw," Buchholz said. "Two-seam wasn't sinking as much as it has been just because I felt like I was getting through it a little too much. But other than that gave up a couple of hard hit balls, but they were early pitches in the count and one of them only was a hit. So, got two quick outs that way, and I'll take that any time."
The Red Sox used six pitchers, with Brian Shouse (1-0) getting the win with a hitless, scoreless inning, and Bowden earning the save, despite laboring through the final two innings, with a run, a hit and three walks.
"Michael Bowden had a tough time pitching, throwing strikes," Red Sox manager Terry Francona said. "He worked behind, and except for the play that we drew up at the end, we were getting in a little bit of trouble. Up till then I thought everybody, Clay included, attacked the zone. ... It was really good. Threw the ball to the plate, let our defense work."
With one out in sixth, Delwin Young hit a solo home run, his second home run of the spring, off Boof Bonser, who is competing for a job in the Boston bullpen, putting the Pirates ahead 1-0.
The Red Sox went ahead in the seventh, with three runs off Chris Jakubuaskas, with the Pirates adding a run in the ninth off Bowden.
Daisuke Matsuzaka was scheduled to throw batting practice Saturday morning for the first time this spring after being delayed by a back ailment. But, a stiff neck scratched that plan after he threw a handful of warm-up pitches in the bullpen.
"I did not throw live BP today due to stiffness in my neck," said Matsuzaka, in a written statement left with a team spokesman. "As for my schedule going forward, I'm going to see how I feel tomorrow, meet with the coaching staff, and decide at that point."
It is not yet known when he will pitch next.
"He was starting to warm up, threw about five or six pitches, and his neck kind of spasmed on him," Francona said. "He talked to (pitching coach) John Farrell, with (translator) Masa (Hoshino) there and decided to shut it down. So we'll go kind of day to day on it."
The neck ailment is not believed to be related to the back problem.
Because of the rainout in their game against the Cardinals on Friday, the Red Sox played an intrasquad game after their game against the Pirates Saturday.