Rumbelow (neck, shoulder) was officially optioned to Triple-A Tacoma by the Mariners on Saturday.
Rumbelow was expected to push for an Opening Day roster spot in the Mariners bullpen, but has been held out with shoulder discomfort since Feb. 24 and more recently is also battling a neck issue. The 26-year-old tossed two-thirds of an inning in his lone appearance of spring training and has no clear timetable for his potential return.