The worst start of Albert Pujols' career continued with one hit in four at-bats — a scratch single off the glove of pitcher Tyson Ross that should have been fielded cleanly.

To make matters worse, the three-time MVP ran himself into an out that same inning after he tried to advance from first to third on a single by Kendrys Morales. But that mistake was overshadowed by a shaky Los Angeles Angels bullpen that squandered a lead for Dan Haren in a 5-3 loss to the Oakland Athletics on Tuesday night.

Pujols' season-opening home run drought reached 11 games and 45 at-bats. The only other time in his 12-year career that he went more than five games before hitting his first homer was 2009, when it took him nine games and 28 at-bats to do it. Pujols is the only player in Major League history to hit 30-or-more home runs in each of his first 11 seasons.

"I don't think he's pressing. He's just trying to get a feel for how he's going to get pitched," hitting coach Mickey Hatcher said. "He's 11 games into the season, and the good thing about him right now is how he goes about his business. You don't see the frustration. What I see from him is that when he comes out of the cage, he says: 'I'm starting to feel it again.' And for him, that's all he wants to do."

Pujols, who signed a 10-year, $240 million contract in December as a free agent, hit seven homers during spring training — including a tape-measure shot at Dodger Stadium that was estimated at 441 feet in his final swing of the exhibition schedule. But so far this season he has only four RBIs and is batting .267.

Pujols averaged 40.5 home runs during his 11 seasons in St. Louis — including a career-best 49 in 2006 — and is the only player in major league history to hit 30-or-more homers in each of his first 11 big league campaigns. Last October he joined Babe Ruth and Reggie Jackson as the only players to hit three home runs in a World Series game.

"I know he wants that first one bad, but the first thing is to just get his swing to feel right," Hatcher said. "He's just trying to get used to the league right now. There have been a couple of pitches on the road and a couple here that he's just missed. But recently, he started to feel like he did in spring training, and he's really happy about that.

"Maybe he's got his mind off of home runs right now and just trying to square it up and get his hits. But the home runs will come. All we want is for him to do is to be a good hitter like Albert Pujols can be, and I think then he'll get hot."

Oakland's Daric Barton ended a career-worst homerless drought of 76 games with a solo shot. Josh Reddick hit a go-ahead RBI double during a four-run eighth-inning rally against Kevin Jepsen (0-1) and David Carpenter, who surrendered a two-run single by Cuban rookie Yoenis Cespedes.

Haren allowed five hits and no walks in 6 2-3 innings after failing to get through six in either of his first two starts. The only run against the three-time All-Star right-hander came in the fifth on Barton's first homer since Oct. 1, 2010, when he hit two against Seattle's Luke French at Safeco Field.

"I know I'm not going to hit 20 or 30 home runs a year," said Barton, who has 27 in 1,495 big league at-bats. "There's been one or two in my career when I knew they were, but I just don't hit them far enough. Most of the time they're line drives and wall-scrapers. I had the feeling this one was gone, but I didn't want to take anything for granted."

The A's got a one-out single from Cespedes and a two-out bunt hit from Kurt Suzuki in the seventh before manager Mike Scioscia brought in left-hander Scott Downs to face the left-swinging Barton — leaving Haren with an 85-pitch outing and a bewildered look on his face.

"I wouldn't have thrown him the same pitch again, that's for sure," Haren said. "He hasn't hit for much power over his career, and that's one spot where down-and-in is probably where his punch is. I've never really had too much trouble with him over the years, so obviously, the competitor in me wanted to face him again. But you could put two and two together."

The move turned out perfectly, as Barton took a called third strike at the knees. But Jepsen gave up a pair of one-out walks, Coco Crisp's tying RBI single and Reddick's ground-rule double, putting Oakland ahead 3-2.

Former Angels closer Brian Fuentes (1-0) pitched a scoreless seventh inning for the victory and Grant Balfour got his third save in as many attempts despite giving up a one-out homer in the ninth by Vernon Wells.

Ross allowed two runs, seven hits and no walks over six innings and struck out three in his season debut after getting recalled from the minors. The right-hander, who turns 25 years old on Sunday, got his chance with the Athletics in need of a fifth starter for the first time season.

Notes: Only a sacrifice fly by Crisp in the final meeting of last season between the A's and Angels prevented Downs from finishing with a perfect 0.00 ERA at home. ... Fuentes, the former Angels closer, has been looking for his 200th career save since June 19, 2011, when he closed out a 2-1 win against San Francisco. He has pitched in the ninth inning four times since then, but not in a save situation.