The Mariners also recalled right-handers Chance Ruffin and Hector Noesi and infielder Carlos Triunfel, and selected the contract of left-hander James Paxton from their top minor league club.
Triple-A hitting coach Howard Johnson was added to Seattle's staff for September.
Mariners manager Eric Wedge said Paxton, who was 8-11 with a 4.45 ERA at Tacoma, will join a six-man rotation the rest of the season. Right-hander Taijuan Walker, who starts against the Royals on Wednesday, will likely get one more start after that before hitting his innings limit.
Wedge said Brandon Maurer will take Walker's spot in the rotation when that happens.
Felix Hernandez was still feeling sore after cramping up in Monday's series opener. He is still scheduled to pitch Sunday but could be pushed back until he's feeling better.
Ramirez was making his ninth start and 10th appearances Tuesday night, while Noesi and Triunfel have also appeared in several games for Seattle. Ruffin hasn't been in the major leagues since 2011, and Paxton will be making his big league debut with his first appearance.
Johnson is completing his first season as a coach with the Mariners.