Marmol, signed as a free agent prior to Spring Training, appeared in 15 games for Miami, going 0-3 with an 8.10 ERA.
At the time Marmol was designated, Miami selected the contract of hard-throwing reliever Henry Rodriguez from Triple-A New Orleans.
Rodriguez made two relief appearances before he was designated on Wednesday. He was outrighted to New Orleans on Saturday.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro. This story was not subject to the approval of Major League Baseball or its clubs.