The Marlins optioned Castano to Triple-A Jacksonville on Monday, Jordan McPherson of the Miami Herald reports.
Castano is expected to slot into Jacksonville's rotation after he made 14 starts for the affiliate in 2021. Injuries opened the door for Castano to make five appearances -- including four starts -- with the big club last season, but he underwhelmed with a 4.87 ERA, 1.48 WHIP and 13:8 K:BB across 20.1 innings.