Arlington, Texas ? Bill Mueller doesn’t understand his record-setting power display.

Mueller became the first player in major league history to hit grand slams from both sides of the plate in a game, connecting for three homers Tuesday to lead the Red Sox over the Texas Rangers 14-7.

“I was just trying to have good at-bats like the guys in front of me,” Mueller said. “I was just trying to drive some runs in. I was fortunate to get some balls up in the air and they carried out. I was just trying to hit line drives, but tonight they went out.”

Mueller, batting left-handed, hit a solo homer in the third against R.A. Dickey.

Batting right-handed, he hit his first slam off Aaron Fultz in the seventh for a 9-4 lead. One inning later, he connected from the left side against Jay Powell for a 14-4 advantage.

“You never come to the ballpark thinking you’re going to do anything like this,” Mueller said. “It didn’t turn out like an ordinary night. I’m very humbled by this.”

Mueller had a career-high nine RBIs with the first three-homer game of his career. He has 13 homers this season, also a career best, and four career slams.

It was the 12th time a player hit two grand slams in a game, the first since Boston’s Nomar Garciaparra in 1999.

Mueller had his second multihomer game this season, the third of his career. He hit two homers against the New York Yankees July 4, connecting from each side of the plate.

Boston, which remained 11/2 games behind the first-place New York Yankees in the AL East, won for the eighth time in 10 games.

Boston's Bill Mueller, left, is greeted by teammate David Ortiz after they scored on Mueller's grand slam in the seventh inning. Mueller hit three homers -- including two grand slams -- against Texas Tuesday at Arlington, Texas.

“There’s a big race in our division and in the wild card,” Mueller said. “We’re focused on winning games.”

Garciaparra and Trot Nixon also homered for the Red Sox, but all the talk in the clubhouse was about Mueller.

“It couldn’t happen to a better guy,” Nixon said. “Coming back from an injury last year and battling back, that’s great for him. I was fired up for him. I was ecstatic. I just wish it would have happened at home just for the ovation he’d get.”

Texas led 4-2 in the seventh when Todd Walker singled off Erasmo Ramirez, and Rosman Garcia (1-1) walked Garciaparra.

Gabe Kapler ended an 0-for-18 slide with an RBI single, and David Ortiz hit a two-run double that put Boston ahead 5-4.

Garcia failed to retire any of the four batters he faced.

Boston starter Tim Wakefield (8-5) had trouble locating his knuckleball, and Doug Mirabelli had four passed balls, two short of the AL record.

Wakefield allowed four runs and six hits in six innings, struck out eight and walked two.

“I had a hard time trying to find my release point,” Wakefield said. “I had to rely on my other stuff and hang in there as long as I could.”

Yankees 6, Angels 2

Anaheim, Calif. — The Yankees bounced back from their bruising weekend series in Boston by winning the opener of their West Coast trip and trading unhappy Raul Mondesi.

Andy Pettitte (13-6) won his career-high eighth straight decision, and Hideki Matsui went 3-for-5 with a home run and two RBIs.

Robin Ventura and Jorge Posada each drove in two runs for New York.

Mondesi angrily left the Yankees’ clubhouse at Fenway Park Sunday night after manager Joe Torre pinch hit for him in the eighth inning and missed the team’s charter flight to California. During the game, New York traded him to Arizona for outfielder David Dellucci and two minor leaguers.

Kevin Appier (7-7) did not make it out of the first inning.

Orioles 7, Twins 5

Minneapolis — Jay Gibbons homered and drove in three runs and Tony Batista also hit a home run for Baltimore.

Gibbons hit a two-run shot in the first, a run-scoring single in the sixth and was at the plate when the Orioles took the lead on a wild pitch in the eighth.

Hector Carrasco (1-2) pitched 11/3 innings. Jorge Julio worked the ninth for his 24th save. LaTroy Hawkins (8-3) took the loss.

Devil Rays 9, Blue Jays 8

Toronto — Rocco Baldelli hit a go-ahead two-run single in the ninth inning as Tampa rallied for a victory. Travis Lee and Aubrey Huff homered for the Devil Rays, who rallied from 4-0 and 7-6 deficits. Toronto’s Carlos Delgado hit his AL-leading 31st homer in the ninth, cutting the lead to 9-8.

Mariners 11, Tigers 5

Seattle — Edgar Martinez, Bret Boone and John Olerud hit home runs, and Gil Meche ended a personal four-game losing streak for Seattle.

Boone went 3-for-4 and had four RBIs, while Martinez and Olerud each had three RBIs for the AL West-leading Mariners, who bounced back after losing two in a row at home to Texas.

Meche (11-7), who hadn’t won since June 26, pitched six innings and allowed three runs on seven hits and three walks, with four strikeouts.

Bobby Higginson homered off Julio Mateo in the eighth for the Tigers, whose record fell to 28-76, worst in the majors.

Athletics 6, Indians 2

Oakland, Calif. — Mark Mulder had 11 strikeouts while pitching into the eighth inning for Oakland.

Ramon Hernandez had a two-run double in the seventh as the A’s scored five late runs to avoid wasting another sterling start from Mulder (14-7), who joined Toronto’s Roy Halladay and Baltimore’s Sidney Ponson as the AL’s 14-game winners.

Keith Foulke finished up for his 27th save in 31 chances.