Per Phil Miller of the Star-Tribune, Sano has been sent to High-A Fort Myers to work on correcting his game.
Things have been off for Sano all season. He missed 25 games in April and May with a hamstring injury while posting a .203/.270/.405 slash line in 37 games prior to Thursday.
Per FanGraphs, Sano's minus-0.2 wins above replacement rank 112th out of 128 AL hitters with at least 150 plate appearances.
After making his MLB debut in 2015, Sano looked like a budding superstar when he finished third in AL Rookie of the Year voting with 18 homers in 80 games.
Last season saw Sano make the All-Star team for the first time when he hit a career-high 28 homers and tied for the team lead with a .507 slugging percentage.
The Twins had high hopes in 2018 after reaching the playoffs as a wild-card team last season. Their 29-36 record is third in the AL Central, six games behind the Cleveland Indians.