Sheffield cleared waivers and was outrighted to Triple-A Tacoma by the Mariners on Thursday.
Sheffield got the boot off the 40-man roster last week to open up a 40-man roster spot for Tommy La Stella. A former top prospect, Sheffield holds a career 5.47 ERA in 186 innings (33 starts, 15 relief appearances) at the major-league level. It's certainly notable that he didn't draw much interest from other MLB teams on the waiver wire leading into what will be his age-27 campaign.