Jered Weaver won his sixth straight decision in the opener, leading the Angels to a 4-2 win.

"It's a tough loss," Hunter said. "Going 0-for-8, that's not going to help the team. It's the third game after the break and we'll get it going. We haven't lost anything. When you're off for a few days it might take some players or teams a little more time."

This was the first planned doubleheader in the big leagues since Aug. 2, 2003, when San Diego played at Philadelphia. Since then, twin bills have been part of makeup games. And it was Oakland's first scheduled doubleheader at home since Aug. 10, 1997, against Milwaukee.

Sizemore hit a 2-2 pitch from Rich Thompson (1-3) to score pinch runner Cliff Pennington from second.

"I just battled until I got a pitch I could handle, put a good swing on it and found a hole," Sizemore said. "Any win is a good win, especially starting the second half. We need to build momentum."

Brad Ziegler (3-1) pitched a scoreless inning.

Mark Trumbo homered and drove in two runs and Vernon Wells also connected for the Angels.

"We didn't hit the ball well all afternoon and we're lucky to come out with a split," Angels manager Mike Scioscia said. "We have guys who can drive the ball with bigger swings and with that comes more strikeouts. As we move forward, hopefully we'll become more of a situational hitting team."

David DeJesus, Landon Powell and Coco Crisp also drove in runs for the A's.

Angels starter Ervin Santana allowed three runs -- two earned -- and a season high-matching 10 hits over 6 1/3 innings. He walked two and struck out six as he remained winless in his past six road starts.

A's pitcher Rich Harden, making his third start since coming off the disabled list on July 1, gave up three runs on four hits over seven innings. Harden walked two and struck out nine.

Trumbo's two-run shot, his 18th home run, in the second inning gave the Angels an early edge. He leads all AL rookies in homers.

Harden set down 11 of the next 12 hitters he faced before Wells' 14th homer of the season tied the score in the sixth.

The A's tied the game at 2 in the fourth, getting RBI singles from DeJesus and Powell. Crisp gave Oakland the lead an inning later with a groundout, allowing Eric Sogard, making his first appearance of the season, to score after an error moved him to third.

Angels reliever Hisanori Takahashi shut down the A's in the seventh after Sogard doubled, Jemile Weeks beat out an infield single and Crisp moved both runners up with a sacrifice. Takahashi struck out Ryan Sweeney, walked Josh Willingham intentionally and struck out DeJesus to end the threat.

A's relievers Grant Balfour, Andrew Bailey and Ziegler kept the Angels off the scoreboard the rest of the way.

Takahashi pitched 2 2/3 scoreless innings.

Erick Aybar homered and Bobby Abreu drove in two runs in the opener for the Angels.

Weaver (12-4), the AL starter in Tuesday night's All-Star Game, did not give up a hit until the fifth inning. He allowed two runs and seven hits in 6 2/3 innings.

"After a few days off I needed to get a feel for the speed of the game again," Weaver said.

Scott Downs got four outs and All-Star rookie Jordan Walden pitched the ninth for his 21st save in 27 chances.

Trevor Cahill (8-8) lasted seven innings, allowing three runs on five hits. He walked five and struck out eight.

"Not being around the field for a while, it was kind of an awkward feeling," Cahill said. "It took a while to get back into things. Maybe that's why I was so erratic in the first inning."

Game notes
Harden last struck out nine or more on May 3, 2010, in Oakland when he was a member of the Texas Rangers. ... Santana's 13 wins over the A's are his most against any team. ... Sizemore broke an 0-for-18 streak with a bunt single in the third. ... The Angels last played a scheduled doubleheader on Sept. 9, 1978, against the Kansas City Royals.