MIAMI -- After the bullpen picked up six innings on Tuesday in a 12-2 loss to the Astros, the Marlins made a series of roster moves, including placing veteran reliever Junichi Tazawa on the 10-day disabled list with rib cartilage inflammation.
The struggles in the rotation have the Marlins considering moving David Phelps, one of their top relievers, into the rotation. The club has already approached Phelps, and he could be a candidate to fill Koehler's spot, which comes up on Sunday vs. the Dodgers in Los Angeles.
"That would be, obviously, something that would be under consideration," manager Don Mattingly said. "But the thing we've talked about with him is not bouncing him around, back and forth."
President of baseball operations Michael Hill has expressed that if Phelps' role changes, the decision would be to keep him in the rotation.
"If we move him towards the rotation, which he said he'd be willing to do what the team needs," Mattingly said, "the one thing Mike has talked about is not moving him to the 'pen at that point. If he goes into the rotation, he stays in the rotation."
Phelps has logged 20 innings in the bullpen this year, but he has 64 career MLB starts. In 2016, his best big league season, the right-hander had a 2.28 ERA, appearing in 64 games with five starts.
The Koehler decision was announced on Tuesday night after the 30-year-old gave up eight runs in three innings vs. the Astros, which raised his ERA to 7.04.
Miami's rotation has been shorthanded due to injury. Wei-Yin Chen is on the DL with left arm fatigue. While he received encouraging news -- that an MRI didn't reveal anything significantly different -- he still is pitching with a partial ulnar collateral ligament tear.
"According to the MRI, they didn't see any obvious problems," Chen said through his interpreter, adding he still is open to getting a second opinion.
Added Mattingly: "They don't see … anything a whole lot different. But the bad news is he's having discomfort when he throws."
Despaigne gives Miami a long-relief/spot-start option, and Ellington adds bullpen depth.
Colon, formerly with the Royals, was claimed off waivers on Tuesday.
Tazawa has appeared in 16 games and has a 6.60 ERA in 15 innings. The right-hander yielded a grand slam to Yuli Gurriel in the sixth inning of Monday's 7-2 loss to the Astros. After the inning, Tazawa was seen in the dugout talking with the trainers.
"I think everybody the other night saw he was kind of having trouble getting his breath," Mattingly said. 'We'll see how that goes."
Joe Frisaro has covered the Marlins for MLB.com since 2002. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.