The Pirates sent eight batters to the plate in the sixth inning, scoring three runs off left-hander Brian Johnson, who left the game with a sprained left big toe.
Pittsburgh right-hander Ryan Vogelsong went four innings, giving up one run on four hits with no walks and two strikeouts. The only run he allowed was Sandoval's homer with one out in the second.
"Pablo got me there. I've seen him hit that ball plenty of times," said Vogelsong, who was teammates with Sandoval in San Francisco. "He probably knew I was going up there. I knew I was going up there. It was just a matter of if I was going to get it by him or not."
In his third spring start, Red Sox right-hander Joe Kelly went four scoreless innings, giving up three hits and a walk with three strikeouts and a hit batter.
"It felt obviously better than I had the previous two times," Kelly said. "I was focused on getting my rhythm and timing back. The first two times I went out there I was a little bit slow, windup was way too slow, stretch was way too slow. So it's something I worked on in between starts just to speed up the tempo. ... Ultimately I threw the ball with more consistency where I wanted to throw it."
David Ortiz went 1 for 3, but ended two innings, including a ground out in the fifth with the bases loaded.
Early in spring training, manager John Farrell called Joe Kelly the leading candidate for the fifth spot in the rotation. Farrell was pleased with the progress the right-hander has made this spring.
"I thought he did a better job with the rhythm inside his delivery after making the adjustment in the final inning last outing and carried it through today," Farrell said. "I thought he threw a number of quality fastballs that either he just missed being off the plate. He made a couple of big pitches with guys in scoring position."
For Vogelsong, who is expected to be the Pirates' fifth starter, it was his third spring outing. He gave up three runs in three innings to the Red Sox in his previous outing.
"I commanded all of my pitches today. I was much sharper than I was the other day and kept my pitch count where it needed to be," Vogelsong said. "It's all about repeating my delivery."
Red Sox: LHP Brian Johnson, a candidate for the rotation, left the game with a left big toe sprain. A fluoroscan was done. "There's not any evidence of anything other than tendon involvement," Farrell said. Johnson will be checked again on Tuesday. ... LHP Eduardo Rodriguez suffered a subluxation of his right knee on Feb. 27. He has not pitched from a mound since. Farrell said on Monday that Rodriguez is getting closer to a bullpen session. ... RHP Carson Smith has not pitched in a game since March 6 while he dealt with back spasms. He is scheduled to pitch Tuesday against the Yankees.
The Pirates assigned RHP Tyler Glasnow and Jameson Taillon Triple-A Indianapolis. RHPs Chad Kuhl and Trevor Williams, LHPs Steven Brault and Kelvin Marte and C Reese McGuire were reassigned to the minor-league camp. Outfielder Harold Ramirez was optioned to Double-A Altoona.
RHP Daniel Bard pitched a perfect ninth with one strikeout to earn his first save of the spring. Bard was a first-round (28th overall) pick by the Red Sox in 2006. He last pitched in the big leagues in 2013, with the Red Sox. His career has been derailed by wildness and injuries.
"You really have to admire his perseverance," said Farrell, who was Bard's pitching coach with the Red Sox. "The last four or five years it's been a long road for him, through the thoracic outlet, the surgery that followed, the adjustment to the arm slot, which looks like he's gaining some comfort with. So you're happy for him to see him back in a big league environment and throwing the ball well."