Right-hander Shun Yamaguchi, who plays for the Triple A affiliate of the San Francisco Giants, revealed that he will return to Japan in an Instagram post on Wednesday.
The 33-year-old signed a minor-league deal with the Giants in February and has played for the Sacramento River Cats. He is expected to exercise his opt-out clause as he seeks to restart his career in Japan.
"I...have decided to return to Japan," he wrote. "I came here chasing my dream of playing in the majors but I will be going back midseason having failed to perform.
"I'm proud of the best efforts I gave despite the restrictions and strict protocols that I've had to play under since last season, and feel strongly about having to make full use of these experiences."
After 14 seasons in NPB, including the last three with the Tokyo-based Yomiuri Giants, Yamaguchi moved to MLB, joining the Toronto Blue Jays through the posting system in the 2019 offseason.
But in his first season in the United States, a pandemic-shortened 60-game slate, he went 2-4 in 17 relief appearances with an 8.06 ERA, and he was released in February this year. He was assigned to the River Cats in May and had hoped to play well and earn a call-up.