"They're big personalities on this team, and obviously their gloves come with them regardless, but we feel it a little bit when they're struggling," manager Bob Melvin said. "They came up big for us tonight. They've both been working really hard in the cages. The expectations for younger guys sometimes are a little too much based on their talent level, but both of them were significant tonight."
Olson smacked his fifth homer -- but just his second in four weeks -- and Chapman enjoyed his first multihit game of the month en route to an 11-hit performance for the A's. Matt Joyce and Khris Davis also homered in support of starter Sean Manaea.
Olson entered the day hitting .156 over his last 20 games, Chapman .135 in his previous 25.
"We've both been struggling a little bit, obviously, and we both need to relax a little bit and stay within ourselves, not try to do too much, so it was nice," Olson said. "You want to go out and perform, and things can start to snowball a little bit when it starts going bad, and you play it out in your head and it's a little worse than it actually is, and you just have to hit reset and check yourself and go day by day."
Manaea put forth a gritty effort in a place that has given him nightmares, yielding four runs (three earned) on eight hits in six-plus innings. He had allowed a combined 15 runs over 6 1/3 innings in his previous two starts at Fenway.
"Especially with the history I've had here, it was really nice to go out there and limit the damage," Manaea said. "Those are the kind of things I've been working on this year, taking a step back and taking a breath and calming myself down and trying not to speed things up, so I feel like I did a really good job of that."
Joyce got the A's on the board in the third inning with a solo homer off right-hander Rick Porcello, but the Red Sox responded with two in the home half against Manaea, who no-hit them in Oakland on April 21.
The A's found their way back on top, 4-2, with a three-run fourth, getting a two-run double from Jonathan Lucroy and a run-scoring triple off the bat of Dustin Fowler for his first career RBI. Boston would again answer in the fifth, the A's would do the same in the sixth via Olson's home run, and it would go on like this.
Manaea offered up a home run to Rafael Devers in the seventh ahead of his departure, then the A's got one of their own from Davis in the eighth, and the Red Sox pulled within one in the eighth on J.D. Martinez's leadoff homer.
Oakland closer Blake Treinen picked up his seventh save with a scoreless ninth.
"If you think you're going to score three, four runs and just hold on, that's not the case," Melvin said. "These guys in late innings are really tough. That's when they get their best at-bats, so they kept fighting back. Ollie's homer was big, K.D.'s homer was huge, especially when Martinez hits that home run, so all in all, a really good game for us today."
SOUND SMART Six of Davis' last 10 hits have been home runs, and 10 of his last 14 hits have been for extra bases. He's a .329 career hitter in 19 games against Boston, marking his highest average against any American League opponent.
YOU GOTTA SEE THIS Olson's homer off Porcello on a full-count fastball offering was clocked at 112.2 mph off the bat, tied for the third-highest exit velocity on an A's homer this season.
"I've been missing a lot of fastballs, so to be able to get on top of that one and drive it was really nice," Olson said. "There's been many times where it's squaring up one or two and I've been back, so hopefully I can take this same approach into tomorrow and I can get going."
HE SAID IT "Pretty tough place to pitch. You're not going to go out and throw a no-hitter against them. [Manaea] kept the lead, never relinquished it, and then turned it over to the bullpen. You leave with a lead in this ballpark, that's a good job." -- Melvin
UP NEXT Right-hander Daniel Mengden (2-4, 4.06 ERA) gets the nod in Tuesday's 4:10 p.m. PT tilt against the host Red Sox. Mengden faced them in a home start earlier this season, settling on a no-decision after allowing one run and six hits with five strikeouts across 6 1/3 innings. Boston will send lefty Eduardo Rodriguez (3-0, 4.58) to the mound.
Jane Lee has covered the A's for MLB.com since 2010.