TEMPE, Ariz. -- Andrew Heaney's comeback from Tommy John surgery will have to wait until 2018.
Manager Mike Scioscia said Thursday that Heaney will likely miss the entire season as he works his way back from ligament surgery on his left elbow.
"From the information I have right now, there is nothing that would make him available to pitch this year," Scioscia said.
Scioscia said the Angels would only change their plans if Heaney's doctors cleared him before the end of the season.
"If doctors evaluate it differently, that's their decision," Scioscia said, "It's not our call or Andrew's call."
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Heaney, 25, made just one start for the Angels in 2016 before partially tearing his ulnar collateral ligament. He hoped to avoid surgery by undergoing stem-cell therapy, but his elbow did not respond to the treatment.
• While stem-cell therapy did not yield the results that the Angels had hoped for with Heaney, it did work for right-hander Garrett Richards, who avoided Tommy John surgery after suffering a partial UCL tear last year.

Richards said Tuesday that he feels healthy and ready to return to the Angels' rotation, but there isn't a lot of precedent for pitchers who have successfully come back from stem-cell treatment.
Still, Scioscia said there are similar cases that the Angels can look to in order to set goals for Richards, such as Yankees ace Masahiro Tanaka. Tanaka was diagnosed with a partial UCL tear in his right elbow in July 2014 and opted for platelet-rich plasma (PRP) therapy and a rehab program instead of surgery.
"It's uncovered territory with Garrett, but we have some guidelines that have been established with some pitchers that have had similar rehabs as Garrett did," Scioscia said. "I think the confidence is very high that he is going to move forward from the injury and be fine. But I think we need to be diligent on just the attention to detail of where he is and how he's feeling."
Tanaka and Richards aren't perfect comparisons, however. Richards received a stem-cell injection in May, followed by a PRP injection in October; Tanaka received only a PRP injection. 
"The fact that [Richards] has something even more advanced might bode better for him," Scioscia said. "We'll see. It doesn't mean that you grow aggressive because he had stem-cell or he had PRP. Where he is is where he is, but there's some data that says that the way he healed up to where he is right now is very reassuring that he's past this."
• Scioscia said the Angels view right-hander Alex Meyer as a starter, meaning he'll likely open the season in Triple-A if he's unable to earn a spot in the Major League rotation.
• Right-hander Deolis Guerra accepted the Angels' outright assignment and arrived at camp Thursday. Guerra had been designated for assignment last week and could have elected free agency after clearing waivers.