The Marlins optioned de Geus to Triple-A Jacksonville on Monday.
De Geus appeared in seven games after being called up by Miami on Aug. 9, giving up five runs (four earned) on seven hits and two walks while striking out four across 5.2 innings. The reliever will head back to the minors to clear a spot in the bullpen and on the 26-man active roster for right-hander Mike Baumann, whom the Marlins claimed off waivers from the Angels on Sunday.