The Angels announced the potentially serious injury for their two-way rookie sensation on Friday before opening a road trip in Minnesota. Ohtani, who will turn 24 next month, underwent injections of platelet-rich plasma and stem cells Thursday in Los Angeles.
The Angels said Ohtani's ulnar collateral ligament has a Grade 2 sprain, which typically indicates some degree of damage but not a complete tear. Ohtani's injury doesn't always require surgery, while Grade 3 sprains are usually repaired by Tommy John surgery.
If the PRP and stem-cell processes do not work, Tommy John surgery is a possibility. Asked whether Ohtani can avoid that, Angels general manager Billy Eppler said, "We're hopeful that he can, that it is completely treatable with the biologic prescription the doctors recommended."
"I'm just going to take every day as it comes and put him on this course of recovery and strengthening for the next three weeks and then deal with what we've got to deal with in three weeks' time," Eppler added.
Manager Mike Scioscia expressed a similarly measured reaction.
"The schedule doesn't stop, and you can't take a timeout," Scioscia said, adding: "We've got to absorb it and move on."
As a rookie with the New York Yankees in 2014, right-hander Masahiro Tanaka missed more than two months because of a partially torn UCL, but he was able to rehabilitate the injury rather than have Tommy John surgery. Ohtani's Angels teammate Garrett Richards also was able to avoid the procedure after suffering a similar injury in 2016 and opting for stem-cell treatment instead.
"Hopefully, this works for him. It worked for me," Richards said. "I understand it doesn't work for everybody, but our thoughts are with him and we're going to be right there with him every step of the way."
Documents made available in December showed that Ohtani had a Grade 1 sprain of his UCL, but Eppler said at the time that there were "no signs of acute trauma" in the ligament.
Ohtani left his last pitching start after four innings Wednesday against Kansas City, but the Angels said it was due to the reoccurrence of a blister on his pitching fingers. Ohtani also left his only loss of the year against Boston in April due to a blister.
Eppler said that while Ohtani was getting treatment for the blister, he mentioned that his elbow was stiff.
"As the game adrenaline wore off, he said, 'My elbow is getting a little stiff,'" Eppler said.
The Japanese right-hander is 4-1 with a 3.10 ERA in his debut North American season, getting 61 strikeouts with a dazzling mix of 100 mph fastballs and precipitous breaking pitches. The Angels' opponents are batting just .202 in his nine starts.
Ohtani also is batting .289 with six home runs and 20 RBIs as baseball's most successful two-way player in decades. The designated hitter has cooled off only slightly after an impressive start at the plate, batting .257 with two homers since April.
Eppler acknowledged that if Ohtani were only a hitter, he "probably" would be able to keep playing with such an injury.
"But that's not his circumstance, and that's not how we want to utilize the player," Eppler said. "It was determined that any unique swing or variability [in Ohtani's elbow] could impose some small percentage increase in risk, so that's why we're going to give it the three-week time period right now to assess and then make a determination at that time."
The Angels have tried to keep Ohtani fresh by giving him at least a week of mound rest between his pitching starts, adhering to a disciplined plan drawn up by Eppler. Although Ohtani was eager for more playing time, the Angels didn't want to rush him into a frantic pace in his first big-league season.
Among pitchers with at least five starts this season, Ohtani has the third-highest average velocity on fastballs (96.8 mph) behind Luis Severino and Noah Syndergaard (both 97.6), according to ESPN Stats & Information.
Any long-term absence for Ohtani could be crushing to a team trying to keep pace with surprising Seattle and defending World Series champion Houston in the high-speed AL West race. The Angels have been using a six-man rotation, so they could probably withstand his absence from pitching better than hitting because they are short on left-handed hitting.
"We're losing two significant parts to our club," Scioscia said. "I think what he did on the mound obviously up to this point is really special, and that's important to us. And what he does in the batter's box, being a left-handed bat, is very important to us."
Information from The Associated Press was used in this report.