Ramirez didn't appear in a spring training game and started the season on the disabled list because of a strained right lat.
Seattle made the move before Sunday's game. Guillermo Heredia, one of five outfielders who had been on the roster, was optioned to Tacoma to make room on the 25-man roster.
The remaining outfielders are Dee Gordon, Mitch Haniger, Ben Gamel and Ichiro Suzuki. Ichiro, 44, was hitting .212 with seven singles and no walks in his 11 games before starting Sunday in right field.
Heredia was hitting .310 with two homers in 16 games.