Kelenic, who is ranked as the No. 3 prospect in baseball according to ESPN's Kiley McDaniel, is hitting just .096 with 26 strikeouts in 23 games. He has two home runs and six RBIs.
He was hitting .370 with two home runs and five RBIs in six games for Tacoma before he was called up to the majors last month.
Kelenic, 21, was selected by the New York Mets with the No. 6 pick in the 2018 amateur draft and traded to the Mariners in the deal that sent second baseman Robinson Cano and closer Edwin Diaz to New York.
In late February, Kelenic indicated that his service time was being manipulated by the Mariners based on comments from Kevin Mather while he was team president and CEO that drew the ire of the MLBPA.
In other moves Monday, the Mariners reinstated infielder Shed Long Jr. (right shin fracture) from the 60-day injured list and transferred infielder/outfielder Sam Haggerty (right shoulder inflammation) to the 60-day IL.