John Maine, a non-roster invitee who opened the season with the Marlins, was designated for assignment on Friday.
In four relief appearances, the 31-year-old posted a 12.27 ERA in 7 1/3 innings.
Tom Koehler was called up from Triple-A New Orleans to fill the long-relief, emergency starter role.
The Marlins are off to a rough 3-13 start, and like the team, Maine has had his struggles.
The veteran right-hander threw two innings in Thursday's 11-1 loss at Cincinnati. He was tagged for six runs on four hits in two innings with five walks and three strikeouts.
Maine broke in with the Orioles in 2004, and from 2006-10, he pitched for the Mets before experiencing shoulder problems.
Koehler made three starts for New Orleans, and in 17 innings he has a 1.06 ERA with 14 strikeouts and 10 walks.
The 26-year-old made his big league debut with Miami last September. He appeared in eight games with one start, and struck out 13 in 13 1/3 innings.