"I feel sorry for not being able to play in the WBC," Ohtani told the Japanese media after the Fighters worked out on Friday in Peoria, Ariz. "I called manager Kokubo yesterday and apologized that I wouldn't be able to play. Originally I thought I was going to get better and I was trying to get ready. But I couldn't.
"Me being out means that they have to find somebody else to play and that takes some time. I thought this was the right moment for me to make a decision, so I did."
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Ohtani sustained the injury during the Japan Series in October, and he experienced prolonged pain that forced him to train away from the Fighters, who began Spring Training this week in Arizona.
"I watched the WBC when I was young," Ohtani said. "I always wanted to wear the Japanese uniform. The tournament is something really, really special to me. I feel very sorry about not being able to take part in it."
A two-way player -- as both a pitcher and a power hitter -- Ohtani is widely considered one of the top players who isn't in the Majors, and he had been touted as one of the must-see attractions of the World Baseball Classic.
On Tuesday, Ohtani said he would not pitch in baseball's premier international event, but he left open the possibility he might still contribute as a designated hitter.
In 104 games last year for the Nippon-Ham Fighters of the Japan Pacific League -- for which he was the league MVP -- Ohtani hit .322 with 22 homers, 67 RBIs and an impressive 1.004 OPS. He also contributed 140 innings on the mound, going 10-4 with a career-low 1.86 ERA and 11.2 strikeouts per nine innings.
Before sustaining the injury, Ohtani was expected to be the ace of Japan's staff in the World Baseball Classic, with Yu Darvish and Masahiro Tanaka not competing. Japan must file its final WBC 2017 roster by Monday.
The two-time Classic champions begin Pool B in Tokyo against Cuba on March 7, then play Australia the following day and China on March 10.
Daniel Kramer is a reporter for MLB.com based in Denver. Follow him on Twitter at @DKramer_. This story was not subject to the approval of Major League Baseball or its clubs.