The Royals recalled Castillo from Triple-A Omaha on Thursday. He'll start the Royals' series opener at Tampa Bay.
Castillo will fill the vacancy in the rotation that was created when manager Mike Matheny moved Brad Keller to the bullpen Wednesday. One of two prospects the Royals acquired from the Blue Jays in the deadline deal that sent Whit Merrifield to Toronto, Castillo will be joining the Royals for the first time after he allowed five runs (four earned) on seven hits and three walks in 3.2 innings over his initial two outings at Omaha. He performed far better in nine appearances (two starts) at the big-league level with Toronto earlier this season, turning in a 3.05 ERA, 0.97 WHIP and 20:5 K:BB across 20.2 innings. Unless he flops badly Thursday, Castillo is likely to make multiple turns through the rotation as the Royals look to assess whether he fits into their long-term nucleus.