The Marlins plan to officially designate Marmol for assignment on Sunday. The club will make a corresponding move to replace the right-hander in the bullpen.
With two 40-man spots open, the club may decide to select the contract of hard-throwing right-hander Henry Rodgriguez, who is at Triple-A New Orleans. Rodriguez was a Spring Training non-roster invitee who didn't make the Opening Day roster.
"It's been a struggle for [Marmol]," Miami manager Mike Redmond said. "We've tried to keep getting him in there in different situations. It just hasn't work."
Marmol's ERA rose to 8.10 in 13 1/3 innings. The right-hander has struck out 14 and walked 10.
Physically, Marmol dealt with a mild right groin strain earlier in the season, but he says he is fine right now.
"I feel 100 percent," Marmol said. "It didn't work out good."
Miami signed Marmol as a free agent to a one-year, $1.1 million contract shortly before Spring Training started.
The club brought him in to offer veteran experience in a setup role. With the Cubs, he had 117 career saves, but he's always dealt with command issues.
Miami entered Saturday tied for first place in the National League East with the Braves, who were percentage points ahead. The young club has been winning, and has been looking for experienced options to help solidify the bullpen.