Otani has put up MVP pitching and hitting numbers for the Nippon Ham Fighters.
Otani, commonly referred to as the Japanese Babe Ruth, hit .322 with 22 home runs and 67 RBIs in 104 games and had a 1.86 ERA and 174 strikeouts in 140 innings last season.
Injuries to his ankle and thigh sidelined Otani for two months early this season and kept him off the mound for a stretch in July and August. He has still managed to hit .346 with seven homers and 28 RBIs in 51 games this season.
The 6-foot-4, 190-pound Otani, who has a fastball approaching 100 mph with an outstanding slider, pitched 5 2/3 scoreless innings on Tuesday in just his third start of the season.
Otani signed a one-year, $2.37 million contract with the Fighters in December and said he wanted to move to MLB after the 2017 season.
Otani, who will not become eligible for free agency in Japan until after the 2021 season, needs the Fighters' approval to negotiate with a major league club through the posting system before that time.
"We discussed the possibility of me going," Otani said in December. "The club will respect my wishes whenever I decide I want to go."
MLB's new restrictions under the collective bargaining agreement negotiated last fall will cost Otani millions of dollars.
Under the old rules, Otani would have been considered a free agent at age 23 and likely sign a contract worth $150 million or more. Under the new CBA, international players under 25 are subject to the bonus pool system, meaning Otani will only be allowed to sign a minor league contract with a maximum signing bonus of about $10.1 million -- unless he waits a couple of years.
But by all accounts, Otani doesn't care about the money.
"As long as I have enough money to be able to play baseball and am enjoying baseball," Otani told Jon Wertheim of Sports Illustrated in an April profile. "That's all I'm asking for right now."