Haren had a two-start winning streak stopped on Friday in Baltimore, as the Orioles hit him for seven runs (six earned) and seven hits in five innings, dropping him to 15-9 on the year to go along with a 3.24 earned run average.
"I've been searching for a little bit of consistency," said Haren, who exited after five innings plus two batters and allowed six earned runs to go along with four strikeouts. "I'm the same pitcher that threw a complete game shutout five days ago, and it's just frustrating to go out there and give up that many runs."
Haren is 6-2 lifetime versus the Blue Jays with a 5.23 ERA in 10 games (nine starts).
Los Angeles bounced back from a loss in Monday's opener on Tuesday, as Mark Trumbo punctuated a five-run fourth inning with a three-run homer, and the Angels notched a 10-6 victory.
Trumbo added an RBI single for Los Angeles, which remained five games behind AL West-leading Texas. The Angels, however, did close within 3 1/2 games of Boston in the wild card race.
"We don't have any wiggle room anymore," Trumbo said. "It's do or die for us. We're probably going to have to win every game from here on out."
Vernon Wells and Alberto Callaspo drove in two runs apiece for the Angels, while Joel Pineiro (7-7) gave up four runs on nine hits over six-plus innings to record his first road win since June 17 against the Mets.
Brett Cecil (4-10) allowed four runs and six hits in three innings to absorb the loss.
"He started to elevate the ball and didn't have a finishing type of pitch," Jays manager John Farrell said of Cecil.
The Blue Jays will rely on righty Dustin McGowan, who has pitched to a 7.50 ERA in three outings this season without recording a decision. McGowan faced the New York Yankees on Friday and allowed three runs and three hits in five innings of a 5-4 win.
He has faced the Angels six times (four starts) and is 1-3 against them with a 3.54 ERA.
The Blue Jays have split their eight matchups with the Angels this season.