Castillo (1-2) allowed four runs on six hits and a walk over five innings Sunday, striking out three and taking the loss against St. Louis.
Castillo quickly fell behind 1-0 in the first inning and things didn't get much better. He allowed two solo home runs to Tyler O'Neill in the second and fifth innings before Dylan Carlson made it 4-0 with an RBI single. The 28-year-old has now allowed at least four runs in three of his five starts this season. Castillo will carry a 6.29 ERA into next weekend's home outing against the Cubs.