Castano (shoulder) cleared waivers and was sent outright to Triple-A Jacksonville by the Marlins on Thursday, per Jordan McPherson of the Miami Herald.
Miami designated Castano for assignment last week as the corresponding 40-man roster move for its completion of a free-agent agreement with veteran starter Johnny Cueto. The 28-year-old left-hander holds a 3.89 ERA, 1.43 WHIP and 45:28 K:BB ratio in 85.2 career innings at the MLB level.