Tyler Thornburg (elbow) has already begun throwing bullpen sessions.
Jim Henderson (shoulder) began throwing off a mound last week.
Taijuan Walker will compete with Roenis Elias and Erasmo Ramirez for the fifth spot in the Mariners' rotation.
Rockies general manager Jeff Bridich said Saturday that Boone Logan (elbow) is completely healthy.
Reds manager Bryan Price said that Anthony DeSclafani is "certainly one of the favorites to make our rotation."