Castano will get the start in the Marlins' Grapefruit League opener Sunday against the Astros, Christina De Nicola of MLB.com reports.
The southpaw isn't thought to be a candidate for a rotation job for the beginning of the regular season, but Castano is firmly in the mix for a long-relief or swingman role out of the bullpen. The 26-year-old posted a superficially strong 3.03 ERA over 29.2 innings last year in his big-league debut, but his 12:11 K:BB and 4.80 FIP offer a better reflection of his likely upside.