In a rare move by a player, Nishioka asked for the release and is walking away from the rest of his contract. He was owed $3 million next season, and the Twins held a $4 million club option for 2014 with a $250,000 buyout.
"This is an unusual instance only because we obviously had high hopes for him when we bought his rights and brought him over, but unfortunately, it didn't work out for either party's best interest," general manager Terry Ryan said. "So I think it's a good thing out of a tough situation. He requested his release, and it sounds like he wants to play in Japan. And financially, it got us out from underneath."
"I would like to thank the Twins organization for helping me fulfill my dream of playing in Major League Baseball," Nishioka said in a statement. "I take full responsibility for my performance, which was below my own expectations. At this time, I have made the decision that it is time to part ways. I have no regrets and know that only through struggle can a person grow stronger. I appreciate all the support the team and the fans in Minnesota and Rochester have shown me. Arigatou gozaimasu."
Nishioka, 28, has struggled since signing a three-year deal worth $9.25 million after Minnesota won the negotiating rights to sign him in 2010 with a $5.3 million bid.
Nishioka hit just .226/.278/.249 with five doubles in 68 games last year, missing more than two months after his left leg was broken in a collision at second base in just the sixth game of the season.
Nishioka went into this season fighting for a spot on the roster but was sent to Triple-A Rochester in the first round of cuts in Spring Training.
After hitting .245 in 84 games with the Red Wings, Nishioka was given another chance with the Twins, called up on Aug. 5. But he lasted just three games before being sent back down, going 0-for-12 with several miscues at second base. He was outrighted on Aug. 20 and removed from the 40-man roster.
It was a disappointing two years for Nishioka, who excelled in Japan. The switch-hitter was a five-time All-Star and three-time Gold Glove winner with the Chiba Lotte Marines before signing with the Twins.
"It was tough," manager Ron Gardenhire said. "I'm sure it was a tough decision for him. I think he wants to get into a situation where we gets an opportunity to renew it and start over. He understands that it didn't work out for him up here."