Riddle, in his fifth season, appeared in four games for the Twins this season, going 2-for-6 (.333) with a run scored.
"JT did not test positive for COVID. There are a lot of different COVID protocols. JT falls within one of them," Twins manager Rocco Baldelli said. "He'll be also traveling on his own back to Minneapolis where he'll quarantine there for a period of time, and then hopefully by the end of the week, we'll have this resolved with him."
To replace Riddle on the 26-man roster, the Twins selected the contract of catcher Tomas Telis from the taxi squad.
Telis, who spent the 2020 season at the alternate training site in St. Paul, Minnesota, has appeared in 122 career major league games, hitting .230 (58-for-252) with eight doubles, three triples, one home run and 24 RBIs over parts of five seasons with Texas and Miami (2014-18).