The Mariners activated Kirby (shoulder) from the 15-day injured list Thursday.
Kirby is set to make his season debut Thursday with a start against the Astros after missing the first eight weeks of the season with right shoulder inflammation. The righty was dinged for eight runs over 10 frames across three rehab outings but posted a 13:2 K:BB. Kirby threw 64 pitches in his final rehab start, so he's probably looking at a max pitch count in the 75-to-80 range Thursday in Houston.