TOKYO — Emil Brown found a safe way home: hit the ball over the fence.

One day after Brown made a costly baserunning mistake, his three-run homer in the third inning led Oakland over the Boston Red Sox 5-1 today and gave the Athletics a split of their opening two-game series.

Following Major League Baseball’s third season-opening series in Japan, the teams were to head back to the United States on 10-hour flights across the Pacific with a split. The Chicago Cubs and New York Mets split their Japanese series in 2000, as did the New York Yankees and Tampa Bay Devil Rays in 2004.

Boston began its World Series title defense with a 6-5, 10-inning victory Tuesday night, boosted by Manny Ramirez tiebreaking, two-run double. The game might have lasted longer had Brown not been tagged between second and third on his RBI double in the bottom of the 10th.

Ramirez kept hitting today with a solo homer in the sixth, although he struck out three times. He could afford to stand and watch this one, a sure home-run deep into the left-field seats that moved him within nine of joining the 500-home run club.

On Tuesday, he admired his 10th-inning double from the batter’s box, thinking it would clear the fence, then hustled to second.

His homer was one of just three hits off Rich Harden (1-0) who is coming back from three injury-filled seasons and made just four starts last year — none after July 7. The right-hander struck out nine and walked two in six innings.

He did better against the other half of Boston’s power duo, retiring David Ortiz twice, once on a strikeout, and walking him once. Big Papi went 0-for-7 in the series.

Coming in, Ortiz was 4-for-5 against Harden and Ramirez was 2-for-3 with two homers apiece.

Jon Lester (0-1) fell behind in the second on a double by Bobby Crosby and an RBI single by Chris Denorfia.

Mark Ellis led off with a walk and Mark Sweeney singled. Brown jumped on a 1-0 pitch from Lester and drove it over the left-field wall.

Oakland added a run in the eighth off Bryan Corey on Jeff Fiorentino’s RBI single after a double by Kurt Suzuki, a native of Hawaii with Japanese grandparents.

Santiago Casilla, Keith Foulke and Alan Embree followed Harden with a scoreless inning apiece, completing a five-hitter for Oakland, which rebounded from its fourth straight opening-day loss. Foulke threw a called third strike past Ramirez to end the eighth with a runner on second.

Lester gave up four runs, five hits and three walks in four innings.

The crowd was much more subdued than it was during the opener, when Daisuke Matsuzaka pitched in his homeland for the first time since signing a $52 million, six-year contract with Boston before last season.

With the unusual schedule, Boston and Oakland will now resume spring training. The A’s have three exhibition games against San Francisco, and Boston plays three against the Los Angeles Dodgers, including one at the Los Angeles Coliseum on Saturday.

They resume the regular season with two games against each other in Oakland starting Tuesday.