Armstrong was called up by the Indians on Wednesday.
Armstrong has spent most of the year bouncing back and forth between Cleveland and Triple-A Columbus, and will rejoin the major-league club after spending a couple weeks down with the Clippers. During 16 appearances with the Indians this year, Armstrong has posted an ERA of 4.26 with a 1.11 WHIP and should figure to slide into low-leverage roles while he's back in the big leagues.