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.
"Today was actually going to be [Koehler's] day to pitch, so he's ready to go," Marlins manager Mike Redmond said before Friday's game against the Reds. "We'll pitch him out of the bullpen. If we need him as a long guy, he can go multiple innings. Maine ... was kind of filling that role, so he'll take his spot."
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 he pitched for the Mets from 2006-10 before experiencing shoulder problems.
Koehler made three starts for New Orleans, and in 17 innings he had 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.
"It's a fresh arm," Redmond said. "The thought right now is to use him in the bullpen as a long guy."
Stanton can't snap out of slump in Friday's win
CINCINNATI -- Giancarlo Stanton's early season struggles continued Friday night against Cincinnati.
Stanton -- making his second start since being activated from the disabled list with a bruised shoulder -- entered the game with a career .800 average (4-for-5) off of Reds starter Mat Latos but went 0-for-4 with two strikeouts. He has struck out 16 times in 36 at-bats this season and has yet to homer or drive in a run.
"He's just got to keep grinding," Marlins manager Mike Redmond said.
It's possible that Stanton, who was an All-Star in 2012, is trying to do too much, especially on a team that is last in the majors in home runs, runs and batting average.
He had a prime opportunity to drive in a run in the sixth inning with Juan Pierre on third base and only one out, but he hit a fielder's choice to Reds shortstop Zack Cozart, who fired to catcher Ryan Hanigan for the out at home.
Stanton is hitting .162.
"If he tries to do too much, he's going to get himself into trouble. It's easy to say but tough to do," Redmond said. "Believe me, he wants to drive in runs, he wants to hit, he wants them to pitch to him every single time. But in reality, that's not going to happen all the time.
"Part of the development process for him is being able to stay in the zone and only do what he can do. If he tries to carry the weight of the team, he's going to struggle."
Kotchman still recovering from pulled hamstring
CINCINNATI -- Marlins first baseman Casey Kotchman is still nursing the left hamstring that he pulled in a 3-0 loss to the Nationals on April 3.
Kotchman came up lame after grounding into a double play in the second game of the season. Initially listed as day to day, Kotchman was put on the 15-day disabled list.
"He's still the same," Marlins manager Mike Redmond said. "It just takes time. He pulled that thing pretty good. He's progressing, but it just takes time for that thing to heal."
The fact that Kotchman's game is not contingent on speed bodes well for a relatively quick return. The 30-year-old has 14 steals in nine-plus big league seasons.
"Obviously speed is not a huge part of his game, so he can probably come back quicker from that injury than, say, Juan Pierre," Redmond said. "But I'm sure as soon as he's ready to start moving and doing baseball stuff, he will."
Kotchman, a career .261 hitter, is hitless in five at-bats this season.
Mahoney gets start in cleanup spot Friday
CINCINNATI -- Miami first baseman Joe Mahoney, who was reinstated off the disabled list this week, made his first start of the year for the Marlins on Friday against the Reds. He was in the fourth spot in the order behind Giancarlo Stanton.
"He's got a lot of pop, a lot of power," Marlins manager Mike Redmond said. "We don't have a prototypical No. 4 hitter. He would be the closest thing to it."
The Marlins have used different lineups in 16 of their 17 games, including Friday.
"We've run a lot of different lineups out there and we're trying to find a way to just get some production," Redmond said. "It seems that no matter which lineup we roll out there, it just produces the same thing."
The Marlins entered Friday last in the majors in home runs (four), runs (33) and batting average (.208).
"We've had many, many chances to drive in runs and we haven't been able to do it," Redmond said. "Really, it's coming to the point where someone [has got to] step up and drive in some runs -- and the guys who do it are the guys who are going to play."
Mahoney, 26, played in two games for Baltimore last year. He went 0-for-4 with the Orioles, and was 0-for-1 this year with the Marlins heading into Friday's game.
Mahoney did, however, have a respectable Spring Training; he hit .233 with three home runs in 31 plate appearances. He's also 6-foot-6 and weighs 240 pounds.
"He has very limited experience in the big leagues," Redmond said. "But at the same time, this is a great opportunity for him to show what he can do. Hopefully he goes out there and has a big night. That would be fun."
• With his game-winning home run off of Reds closer Aroldis Chapman on Friday night, Justin Ruggiano extended his hitting streak to five games. He is batting .421 (8-for-19) during the streak.
• Through 17 games, only one Marlins starter -- Alex Sanabia -- has recorded a win this season. Sanabia is 2-1 with a 4.24 ERA.
• Marlins reliever Steve Cishek has not allowed a run in eight career appearances against the Reds.
Tony Meale is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.