David Ortiz's milestone 400th home run became one of the few bright spots for Boston on a disappointing 2-5 road trip out West.
Next up is the New York Yankees in a four-game weekend set, and the Red Sox hardly have the momentum they'd hoped for to face their AL East rival in an always-emotional series.
Ortiz hit his 400th homer with a leadoff drive to right in the fourth inning against Oakland starter A.J. Griffin, yet Boston managed little else in losing to the Athletics 3-2 on Wednesday and leaving town with a sweep to carry for the long flight home.
"Our offense has just been terrible," right fielder Cody Ross said. "I don't need to sugarcoat it. It just (stunk) basically. Our pitchers have been pitching their butts off to keep us in games and we just can't seem to push a run across."
After a tough day, Ortiz returned to the clubhouse to some 40 congratulatory messages.
"And my phone is still blowing up," he said. "I know at some point in my career when I'm not playing baseball I might look at it from the outside and be like, 'Whoa, I guess I had a good career.' I look at it right now as just another home run."
The 36-year-old Big Papi's home runs rank eighth among active players and 49th on the all-time list. Next up for him to catch: Hall of Famer Duke Snider with 407.
"I wish he could celebrate," manager Bobby Valentine said. "David is a team guy and he knows it's a great individual accomplishment, we all know that. But it's tarnished."
The A's fans did their part to mark the moment.
Ortiz tipped his batting helmet as his milestone was announced to a standing ovation before he stepped in to hit in the sixth, then drew a five-pitch walk. He was thrilled with the surprising gesture from a crowd of 28,240.
"That was pretty cool. You're playing on the road and you get something like that on the road, where people really appreciate it," he said.
Ortiz's 22nd home run of the season tied the game at 1. He has 352 home runs and 1,142 RBIs as a designated hitter for most all time by a DH.
Red Sox Hall of Famers Ted Williams and Carl Yastrzemski also hit their 400th home runs against the Athletics franchise — both also doing so in July. Williams hit his against the Kansas City A's.
Ortiz also scored on Adrian Gonzalez's sixth-inning single, but Boston couldn't avoid its first sweep by the A's since May 23-25, 2008, also in Oakland. The Red Sox lost just their fourth series in the past 17 and completed a disappointing trek through Seattle and Oakland, the AL West's two bottom teams.
"It was a pretty disappointing road trip," Valentine said. "We battled the whole way but we just didn't get those hits. I really believe we will."
Brandon Moss homered among his three hits for the A's and finished 6 for 8 with five RBIs and three runs scored against his former club that traded him away.
"Playing against a team you came up with and team you played your first little bit in the big leagues is special," Moss said. "You want to do well, not out of animosity, but to show, 'Hey, you did draft a good player.'"
Jemile Weeks hit a go-ahead RBI single in the seventh following Coco Crisp's leadoff triple in Oakland's fourth straight win.
Moss homered leading off the second for his 10th of the season, giving the A's longballs in 15 straight games — most for the club since doing so in 17 in a row from April 12-May 1, 2002.
Moss singled in the fourth and doubled in the sixth, leaving him a triple shy of the cycle. Brandon Inge doubled home Moss to tie the game at 2 in the sixth.
Grant Balfour (2-2) went 1 2-3 innings for the win as the A's (41-42) moved within one game of .500 for the first time since they were 22-23 on May 23. Lone A's All-Star Ryan Cook finished with a 1-2-3 ninth for his eighth save in 11 chances.
Aaron Cook (2-2), coming off a career-best two-hit shutout in a 5-0 win at Seattle on Friday in which he didn't walk a batter for the second straight outing, was tagged for nine hits and three runs in six-plus innings.
Facing Oakland for the first time since June 28, 2009, while with Colorado, the right-hander fell to 4-2 in six career starts versus the AL West.
Second baseman Weeks' fielding error in the sixth led to Boston's unearned run and cost Griffin a shot at his first major league win. Gonzalez's RBI single extended his season-best hitting streak to 15 games, longest active in the majors. He had 10 hits during the trip.
The A's also allowed Paul Konerko's milestone 400th home run for the White Sox when he did it April 25 against Grant Balfour in the Coliseum.