As we reported, Puig had initially agreed to plead guilty to one count of making false statements ... after federal prosecutors accused him of lying about participating in an illegal gambling business during an interview earlier this year.
Puig hoped to avoid jail time with the plea deal ... but now, he's decided to fight the charge and faces up to five years in prison if convicted.
Puig's attorney, Keri Axel of Waymaker LLP, said the course reversal came following the reveal of "significant new evidence" ... explaining that during Puig's interview with the feds, he was in essentially no condition to properly answer their questions.
"At the time of his January 2022 interview, Mr. Puig, who has a third-grade education, had untreated mental-health issues, and did not have his own interpreter or criminal legal counsel with him,'' Axel said.
"We have reviewed the evidence, including significant new information, and have serious concerns about the allegations made against Yasiel.''
Puig -- who's now playing baseball in South Korea after seven seasons in the MLB -- added in a Tweet late Wednesday afternoon, "All my life's I been told to be quiet and do what I was told. No mores."