But the right-hander said on Sunday that he "should be good to go" when the Angels open a two-game home series against the A's on Monday night. Oakland will counter its former ace with Tyson Ross, looking to build on the 3-1 series win it took in Anaheim last month.
Haren (1-3, 4.19 ERA) felt a small pinch in his lower back while he warmed up in the bullpen before his outing against the Twins last Tuesday in Minnesota. He has dealt with the issue before, but this time, he couldn't find a remedy.
"A lot of times you start loosening up throughout the game, and it was kind of the opposite," Haren said after giving up five runs in 3 2/3 innings. "It just progressively got a little bit worse."
Haren threw 78 pitches, allowed eight hits, walked two and didn't record a strikeout. That ended a stretch of four starts in which he posted a 2.17 ERA and held the opposition to 20 hits in 29 innings.
Haren threw a light bullpen session on Friday, played catch on Sunday, then caught an early flight back to Anaheim.
"The only time it really bugs me is when I'm going 100 percent on the mound," Haren said. "I got after it a few pitches in the bullpen and I felt a lot better. I'm trying to just give it as much rest as I can. I'm sure it'll be fine."
Ross (1-3, 7.71) gave up three earned runs in 5 2/3 innings against the Blue Jays last Wednesday. He called the start "definitely a step in the right direction," following two outings in which he surrendered a total of 16 earned runs on 20 hits.
Ross sports a career 5.08 ERA, but that mark is 2.61 in 20 2/3 innings against the Angels, the team he has faced most in the big leagues. He battled Haren to a no-decision on April 17, holding the Angels to two runs in six innings in a 5-3 A's victory.
"He has good stuff," Angels manager Mike Scioscia said after that game. "He pitched tough. He has deception and mixed in some tight sliders and two-seamers. We couldn't break through against him."
A's: Hoping for reinforcements
First baseman/designated hitter Kila Ka'aihue (tight hamstring), third baseman Brandon Inge (tight hamstring), catcher Kurt Suzuki (sore left hand) and second baseman Jemile Weeks (sprained left ankle) all sat out Sunday's game against the Tigers. While Ka'aihue is not yet able to run, the other three could return to the lineup on Monday. Outfielders Yoenis Cespedes and Coco Crisp already are on the 15-day DL.
Since April 25, outfielder Josh Reddick is batting .348 (23-for-66) with six home runs and 16 RBIs, having hit safely in 15 of 16 games.
Ross is 0-1 with a 2.75 ERA in four games (three starts) in Anaheim and 0-0 with a 0.00 ERA (one inning pitched) in one appearance in Oakland.
Angels: Taking a breather
Scioscia didn't start shortstop Erick Aybar or right fielder Torii Hunter on Sunday against the Rangers, giving a pair of struggling players a chance to rest. Aybar has collected one extra-base hit (a double) since April 22 as his OPS has fallen to .470. Hunter is mired in a 2-for-30 skid since racking up three straight two-hit games from April 30 to May 2. As for Hunter, the outfielder has one hit (a homer) in 24 at-bats during his last seven games, dropping his batting average from .297 to .256.
"He drove one ball good to center a couple nights ago, so he's not that far off," Scioscia said. "He's not as comfortable as he was when he started hitting the ball when we came back from New York. He just hasn't had many hits to fall. Everything else looks good, though."
The Angels won seven of their first 22 games but have taken eight of their last 13 heading into Monday.
The Angels are 9-8 at home but only play four games in Anaheim before departing on a 10-game trip to visit San Diego, Oakland and Seattle.
A's reliever Ryan Cook has not allowed a run, and his 16 2/3 innings pitched are the most among American League relievers that have not allowed a run. He has a 17 2/3-innings scoreless streak dating back to last year.
Haren is making his eighth career start against his former team. He is 2-2 with a 3.45 ERA and a 35-to-5 strikeout-to-walk ratio. Haren held Oakland to one run in 6 2/3 innings on April 17. Bill Lachemann, the Angels' special-assignment catching coordinator, lost his wife, Darriel, following complications with respiratory failure on Sunday. The two were married for 52 years and had been tied to the Angels since 1985. The family will hold a "Celebration of Life" gathering toward the latter part of June. Details are forthcoming.