Koch (5-4) allowed five runs on seven hits in a loss to the Angels on Tuesday, issuing two walks and failing to record a strikeout in 5.2 innings.
Koch surrendered a pair of solo home runs to Ian Kinsler and Kole Calhoun, but the major damage came on a bases-loaded single by Mike Trout that plated three runs. In three of his last five starts, Koch has allowed five earned runs, but the other two outings were quality starts. Overall, the 27-year-old has a 4.40 ERA and 1.20 WHIP with a 38:17 K:BB in 71.2 innings. As Shelby Miller and Robbie Ray near a return to the Arizona rotation, Koch may be on the brink of losing his starting role.