Shaw (3-for-5, five RBIs, two runs) finished a triple shy of the cycle. Ramirez added three runs, three hits and two RBIs. Jackie Bradley Jr. added two hits to run his career-high hitting streak to 16 games. The eruption by the offense was impressive on a night David Ortiz got a rest.
"In a number of games this year, we've gotten off to a quick start, and gotten multiple runs in the first, turn it over to the starter with a decent lead," said Red Sox manager John Farrell. "We took good swings pretty much all night long. It's good to see some left-handers hit some left-handers tonight as well. A strong offensive night."
The Red Sox, who downed the A's, 14-7 on Monday, have won 11 of their last 15 games. The A's have dropped 13 of their last 17.
O'Sullivan had an 11-0 lead after five before the A's scored four on him in the sixth. The righty gave up 12 hits and four runs over six innings while walking none and striking out three.
"I've been here before, but I haven't actually pitched here before," said O'Sullivan. "So when I went out there to warm up initially, I looked down getting ready to fix my belt and I saw 'Red Sox' across my chest, and I was like, 'This is pretty cool. Man, how many people get to say they've started a game for the Boston Red Sox in Fenway?' So that was pretty surreal."
Billy Butler led a balanced Oakland attack with three hits. A's lefty Sean Manaea lasted just 2 2/3 innings, giving up 10 hits and eight runs.
"He just made too many mistakes over the middle of the plate," A's catcher Stephen Vogt said. "This is a team that's obviously very, very good offensively, and every single one of them are hot right now, too. That's two nights in a row they haven't missed a mistake, and unfortunately we made a few early that they took advantage of."
MOMENTS THAT MATTERED Hanley's tale of tape: Ramirez's majestic two-run rocket to left-center in the first inning was projected by Statcast™ to land 468 feet away from home plate. Only Giancarlo Stanton's 475-foot shot against the Phillies last week went further. It was Ramirez's fourth homer of the season, but third in the last week.
"Oh yeah? He got lucky. I'm going to beat that," Ramirez quipped when told only Stanton hit a home run with a longer projected distance this season. More >
(Another) A's starter struggles: A night after Sonny Gray was tagged for seven runs in a 14-7 loss to the Red Sox, Manaea was knocked around for eight runs and 10 hits in just 2 2/3 innings, continuing an ugly trend. Oakland starters have yielded 76 earned runs in their last 83 innings for a dismal 8.24 ERA over a 17-game stretch, 13 of them ending in losses.
"Obviously I think we've got the arms to turn it around," Vogt said. "This is definitely a difficult stretch, and our opponents that we've faced haven't been the kindest either. We've faced some really good lineups."
"I was just leaving the ball out over the middle, and they were taking advantage of it," Manaea said. "I felt like I was maybe getting inside, but looking back on it, I was pretty much throwing right down the middle. It's frustrating, because I know I'm a lot better than this." More >
Bradley cuts down run: In the second, the Athletics thought they could cut into Boston's lead on a single by Chris Coghlan. But Bradley had other ideas. The center fielder came up firing, and his throw -- measured at 98 mph by Statcast™ -- was gloved on the fly by catcher Ryan Hanigan. Even though the throw was on the first-base side of the plate, Hanigan had time to snare Bradley's rocket and tag out Butler. It was Bradley's fourth assist of the season, equaling his total from last season.
Silver lining: Though overshadowed by woes elsewhere, the A's offense is noticeably heating up, averaging 5.5 runs over the team's last six games. Oakland totaled 15 hits in Tuesday's loss, getting at least one from every starter and at least two from five players, including Josh Reddick. The A's right-fielder went 2-for-3 to improve to 13-for-19 on the road trip and increase his season average to .325.
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Shaw was just 2-for-25 against lefties this season before Tuesday, when he had two of his three hits against southpaws and all five of his RBIs. More >
WHAT'S NEXT A's: Left-hander Eric Surkamp will be recalled from Triple-A Nashville for Wednesday's start against the host Red Sox in the 4:10 p.m. PT series finale at Fenway Park. Surkamp was 0-2 with a 5.59 ERA in four starts for the A's last month, allowing 12 earned runs and 25 hits in 19 1/3 innings.
Red Sox: Right-hander Rick Porcello takes the ball as Boston tries to complete a three-game sweep of Oakland. Porcello had his five-game winning streak snapped last time out against the Yankees, but he still pitched well, giving up three runs over seven innings.