Armstrong was designated for assignment by the Mariners on Wednesday, Shannon Drayer of 710 ESPN Seattle reports.
A 40-man spot was needed to make the signing of Ichiro Suzuki official, and Armstrong wound up being the roster casualty. The 27-year-old struggled in 24.2 innings with Cleveland last season, producing a 4.38 ERA, but he did have a 3.07 ERA in 29.1 innings with the club's Triple-A affiliate. Armstrong's major-league experience could make him attractive to a few teams.