The Guardians reinstated Armstrong (calf) from the 60-day injured list Wednesday.
Armstrong landed on the 15-day IL with a left calf strain in late July and was later transferred to the 60-day IL. He has now been cleared to return after making four rehab appearances at Triple-A, though Armstrong figures to be eased back in with some low-leverage innings to close the campaign. The veteran righty has regressed in a major way, posting a 4.91 ERA and 1.45 WHIP so far this year after putting up a 2.31 ERA and 0.81 WHIP last regular season.