Armstrong had his contract selected from Triple-A Tacoma on Tuesday, Ryan Divish of The Seattle Times reports.
Armstrong compiled an impressive 1.77 ERA and 82:26 K:BB across 56 innings of relief with Triple-A Tacoma before earning a promotion. He spent time in the majors with the Indians each of the past three seasons, posting a solid 3.53 ERA across 43.1 innings. Nick Rumbelow was sent to the minors in a corresponding roster move.