The former Japanese-language translator for Shohei Ohtani was charged with bank fraud on Thursday for allegedly stealing more than US$16 million from the Los Angeles Dodgers superstar to pay off gambling debts.

Ippei Mizuhara, 39, made a series of unauthorized transfers from Ohtani's checking account between November 2021 and January 2024, the Justice Department said.

US federal prosecutor Martin Estrada told a press conference there was no evidence to suggest Ohtani was aware of or involved in Mizuhara's illegal gambling activity.

"I want to emphasise this point: Mr. Ohtani is considered a victim in this case," Estrada said.

Ohtani, the biggest star in baseball, joined the Dodgers last December in a record-breaking US$700 million deal.

The 29-year-old Ohtani told reporters last month that he has never bet on baseball and had not known previously about Mizuhara's gambling problems.

Ohtani has not said in public how so much money could go missing from his account without his knowledge.

According to the Justice Department, Mizuhara transferred more than US$16 million from Ohtani's bank account "to pay off his own substantial gambling debts incurred with an illegal bookmaking operation."

It said Mizuhara, in 2018, accompanied Ohtani, who did not speak any English at the time, to a bank branch in Arizona to open an account.

"Ohtani's salary from playing professional baseball was deposited into this account and he never gave Mizuhara control of this or any of his other financial accounts," according to an affidavit in the case.

"Mizuhara allegedly told Ohtani's US-based financial professionals, none of whom spoke Japanese, that Ohtani denied them access to the account," it added.

Estrada said that while employed as Ohtani's interpreter, Mizuhara had in fact operated as the baseball star's "de facto manager." (AFP)