Angels pitcher Garrett Richards has not played catch since he was diagnosed last week with what the team called a strained bicep. (Jeff Chiu / Associated Press)

The Angels do not plan to activate ace Garrett Richards from the 10-day disabled list when he is eligible Sunday. Richards has not yet been cleared to resume throwing, and reliever JC Ramirez will replace him in the Angels’ rotation on Friday.

“Right now, there’s no time frame for how long he’ll be in our rotation,” Manager Mike Scioscia said Thursday of Ramirez. “It could be the whole year.”

Scioscia was not suggesting Richards would sit out the whole year, but he did indicate Ramirez would have an opportunity to make more than just the one spot start.

Richards has not played catch since he was diagnosed last week with what the team called a strained bicep. He has not pitched in eight days, and he could require more time to rebuild arm strength and/or complete a minor league rehabilitation assignment, depending on when the Angels’ medical staff clears him to resume throwing.

“They’ll let us know when he’s ready to pick up a ball,” Scioscia said. “The longer he’s out, obviously, there would be more rehab involved.”

The Angels’ postseason chances imploded last season when injuries forced the team to field a patchwork rotation that included such veterans as Tim Lincecum and David Huff. Richards is the key to the Angels’ rotation.

Richards, 28, was limited to six starts last season because of a torn elbow ligament. He successfully rehabilitated the elbow with injections of stem cells and platelet-rich plasma, avoiding the need to undergo reconstructive surgery and sit out a season. Although the bicep strain forced him to miss his first start this season, the elbow appeared sound in a subsequent MRI examination.

Ramirez, 28, will make his first start since 2011, when he was in double-A with the Philadelphia Phillies. Since then, he bounced to the Cleveland Indians, Arizona Diamondbacks, Seattle Mariners and Cincinnati Reds organizations before the Angels claimed him on waivers last June.

When he signed his first pro contract, as a 16-year-old from Nicaragua, he said he envisioned himself as a starting pitcher in the major leagues. He had all but abandoned that goal along the way, but the Angels directed him to work as a starter in winter ball and tried him as a starter in spring training.

Now, he gets his chance to do what he imagined himself doing a dozen years ago.

“Dream come true,” he said.

With Richards out of the rotation — at least for the short term — Scioscia said the Angels would monitor how the bullpen responds without what he called the “multi-inning power arm” of Ramirez. The Angels’ bullpen has worked more innings than all but one American League team.

“We’ll pay attention to where this goes in the next couple weeks,” Scioscia said. “If he lights it up as a starter and helps us win games, great. We have to keep our finger on the pulse of our whole pitching staff.”

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