An MRI revealed Angels ace Jered Weaver has tendinitis in his pitching arm, ruling him out to start this weekend against the Tigers. That tendinitis, however, is in his bicep and isn't directly linked to taking a line drive off his right shoulder in a start against the Mariners on Sunday.

The Angels only expect him to miss one turn through the rotation.

"Quite simply, he has biceps tendinitis and it has nothing to do with being struck with the line drive," Angels general manager Jerry Dipoto said. "He's going to miss his start next time through and should be back shortly thereafter."

Three days after being hit by a fifth-inning Dustin Ackley comebacker in Seattle --- prompting an exit one inning later, despite throwing only 86 pitches -- Weaver left the team in Oakland on Wednesday morning and traveled to Los Angeles, where he received an MRI and was evaluated by Dr. Lewis Yocum, revealing the tendinitis.

Weaver's immediate absence means Ervin Santana will start Friday against Max Scherzer, C.J. Wilson will start Saturday against Justin Verlander and Zack Greinke will start Sunday against Anibal Sanchez. The Thursday off-day allows everyone to be on normal or extended rest.

With Dan Haren tentatively slated to start Monday against the A's, Weaver's next turn through the rotation would come up once again on Tuesday, though the Angels haven't announced how it'll line up past this weekend.

This was going to be a month when the Angels would lean heavily on Weaver, who's 16-4 with a 2.86 ERA and has been the one constant in a star-studded rotation that struggled mightily for several weeks. Weaver was going to start almost every fifth day in September, setting him up to make six more starts and line up for the regular-season finale on Oct. 3.

Those plans have been altered, but for now, the Angels only expect it to affect this weekend.

"He's extremely important to what happens to us today, tomorrow, next year and the year after," Dipoto said. "I don't think that we were taking lightly, just to make sure that he was in a good spot. I'll let you know how relieving it is when he's back out there, but for the time being, we're just going to give him a little blow, skip him this time through the rotation and hopefully get him back on track."

The Angels have received a lot better production from their rotation of late. The staff posted a 5.71 ERA over a 42-game stretch that began July 3 -- a span in which the Angels went 17-25 -- but has posted a 3.19 ERA over the last 15, with the Angels winning 12 of those games.