Angels manager Mike Scioscia said he anticipates Pineiro being ready to make his season debut "somewhere around the eighth" of April "if everything goes good." He hopes to have his veteran right-hander on a mound in camp in about eight days.
Matt Palmer will replace Pineiro on Friday against the Athletics in Phoenix, and the plan is for him to work five innings or throw 75 pitches, whichever comes first.
2010 Spring Training - null
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Spring Training Info
The Angels have days off on April 4 and April 7, which gives Scioscia the luxury of putting a starter on the disabled list to open the season, if necessary. A player can be on the DL for only 10 days to open the season, retroactive to five days before the opener.
Pineiro said he felt "better than when I went out to pitch" the day after the muscle tightness surfaced.
"All my strength is there," he said. "It's just that muscle that had to get loosened up. It's the muscle where it connects to the lat [lattisimus dorsi]."
Comparing it to a "cramp that stiffened up," Pineiro said he would have continued pitching if it had been a regular- season game, but felt no need to push it in spring.
"In a regular-season game, you figure out a way to adjust," Pineiro said.
Pineiro reached 73 pitches in his previous outing and believes he's stretched out sufficiently to get deep in games when the season opens.
He missed six weeks last season with an oblique strain that he said was unrelated to this muscle issue. He returned to finish strong with three September starts and was 10-7 with a 3.84 ERA in 23 outings.
In four Cactus League games, Pineiro is 2-0 with a 3.46 ERA. He has yielded one walk while striking out seven hitters in 13 innings. He pitched two innings in the camp game on Sunday before departing.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.