"I enjoyed it," Watson said. "It was nice to finally get one. I'd like to count some of my Asian ones as major league home runs but I don't think they count in the record book."
Watson came up to the big leagues with the Mets in September 2003 and appeared in 15 games. He was claimed by the A's on waivers that offseason and spent most of the next two years at Triple-A, playing 19 games in the majors.
Watson had his contract sold to Chiba Lotte in Japan in 2006 and hit nine homers in parts of two seasons. He spent 2008 in the minors with the Toronto organization, played briefly in South Korea that offseason and returned to the Mets in 2009.
Let go because of a bad back, Watson played for Lancaster of the independent Atlantic League before the A's brought him back on a minor league deal in May.
"The fact that he's here and did a great job today is what counts," A's starter Gio Gonzalez said. "The road is a beautiful road when you're sitting on the major league level. To hit his first major league home run, it's a beautiful day for Matt Watson."
"We're pointing in the right direction," Gonzalez said. "We have a little streak going on again. We're going to try to keep it going."
The Red Sox are going the opposite direction despite getting Adrian Beltre's second homer of the series. They are 2-5 since the All-Star break and seven games behind the New York Yankees in the AL East.
Clay Buchholz (10-5) was not sharp in his first start for Boston since injuring his left hamstring running the bases in San Francisco on June 26. He gave up a pair of early homers and was unable to record a single out in the fifth. He allowed five runs and six hits to lose for just the second time in his last 10 starts.
"I thought he looked like he had some rust," manager Terry Francona said. "He left a couple of fastballs over the plate that really did a lot of damage. The game was a little quick for him. He'll be OK. He's healthy."
Gonzalez allowed RBI singles to Beltre in the first and Jed Lowrie in the fifth before running into more serious trouble in the sixth inning. Kevin Youkilis led off the frame with a single and Beltre followed with his 16th homer.
After J.D. Drew singled, Oakland's defense bailed out Gonzalez. Davis made a running grab in the gap in right-center to rob Mike Cameron of extra bases. Bill Hall then hit a grounder up the middle that second baseman Mark Ellis tracked down to start a slick double play.
"It's pretty frustrating," Hall said. "We hit it right at people. We have to start pressuring teams earlier. We're not swinging the bat too bad but we're not putting hits together. Pressing is not the answer to our problems."
That ended the day for Gonzalez, who allowed four runs and seven hits.
Henry Rodriguez pitched around a pair of walks in the seventh with a fastball that reached triple digits on the stadium radar gun. Brad Ziegler got three outs and Michael Wuertz had a perfect ninth for his second save.
Buchholz escaped trouble in the first when he got Kevin Kouzmanoff to bounce into an inning-ending double play with the bases loaded. But then Buchholz gave up homers in consecutive innings to the power-challenged A's after allowing just three all season coming into the start.
Watson connected in the second for a solo shot in just his third game since being brought back to the majors July 5. With Ryan Sweeney out for the season with a knee injury, there could be more chances for Watson to play.
"I know I can do it at this level if given an opportunity," he said. "It's just finding a chance and someone that believes in you to give you the opportunity."
Cust added a two-run shot in the third.
In between the two long balls, there were a couple of oddities that didn't affect the score. After Watson's homer, Davis reached on an error when Youkilis dropped a throw from Beltre following a bunt toward third. Davis advanced to second on a balk and third on a wild pitch before being thrown out at home on a grounder to second because of a perfect block by catcher Dusty Brown.
Then with a man on first in the third inning, Kurt Suzuki hit an infield popup that Beltre dropped. But there was no damage as Beltre easily got the force at second base. Cust followed with his sixth homer to make it 3-1.
The A's dropped Coco Crisp from leadoff to ninth in the lineup because he came into the game in a 2-for-27 slump. He went 2 for 4. ... Lowrie made his 2010 debut for Boston after being sidelined since the spring with mononucleosis.
As Toronto looks to add a left-hander to upgrade its bullpen, the Jays are reportedly interested in former Red Sox reliever Robbie Ross Jr.
Baltimore is reportedly eyeing the right-hander, who became a free agent after declining a qualifying offer from the Rays.
Arizona reportedly isn't ruling out a reunion with its closer from last season.
Coming off a career year, the Chicago outfielder is reportedly garnering trade interest from the A's.
San Francisco reportedly has "had discussions" about signing the veteran slugger, but it's unclear if the team has met with agent Scott Boras.
The Oakland Athletics have hired former San Francisco Giants star Matt Williams as their new third base coach. Williams most recently managed the Washington Nationals for two seasons in 2014-15.