MIAMI -- Marlins left-hander Wei-Yin Chen was placed on the disabled list with a left elbow sprain, retroactive to Thursday, manager Don Mattingly announced following Sunday's 3-0 loss to the Mets. The Marlins are hopeful that the injury is not serious.
Right-hander Jarred Cosart is being called up from Triple-A New Orleans to start in Chen's place on Monday against the Phillies in Miami.
In his last start, a loss at Philadelphia on Wednesday, Chen worked 5 1/3 innings, giving up four runs. His fastball velocity reached as high as 94 mph in the fifth inning, but in the sixth, it was around 90 mph.
"Wei-Yin came in after the last start a little bit tender in his elbow," Mattingly said. "We've got to be cautious. We can't afford to let that thing get away from us, so we have to be cautious with him, and bring up Jarred."
Because his disabled-list stint is retroactive to Thursday, Chen is eligible to be reinstated as early as Aug. 6, when Miami is in Colorado.
Chen was scheduled to throw his between-starts bullpen session on Saturday, but that was canceled. The past few days, he's been undergoing some tests, and the team is hopeful a few days of rest will lead to a quick recovery.
"I have been experiencing some soreness in the elbow since the last start," Chen said. "We had some discussion between me, the pitching coach and the manager, and we'll see. We'll give it a couple of days of rest and see what happens."
Chen, who turned 31 on July 21, is 5-4 with a 4.99 ERA in 19 starts. The left-hander's 110 innings pitched are third most on the team.
When he was 21 and playing in Japan, he experienced an elbow issue that led to Tommy John surgery, but he hasn't dealt with any serious issues since.
After he spent four seasons with the Orioles, the Marlins signed Chen as a free agent to a five-year, $80 million deal in January.
The transition to the National League hasn't been completely smooth for the veteran from Taiwan, who was Miami's Opening Day starter. In his first outing, against the Tigers on April 5, Chen was struck on his throwing elbow by a line drive.
He ended up missing one start, but didn't go on the disabled list.
"The team is in the race, and this is a very important time," Chen said. "But for me, I'd like to help the team when I'm 100 percent. I don't want to rush out there when I'm not 100 percent."
Cosart, 26, opened the season in the Marlins' rotation, but he was optioned to New Orleans after going 0-1 with a 7.98 ERA in three starts. At Triple-A, he made 10 starts, posting a 3-4 record with a 4.09 ERA. The right-hander also spent time on the Minor League disabled list with an oblique injury.
Monday is a big opportunity for Cosart, who is a hard-thrower but has been hindered by command issues, walking 15 in 14 2/3 innings before he was optioned to New Orleans.
Cosart, however, has experienced big league success. He's 16-18 with a 3.74 ERA in 57 MLB appearances, with 56 starts.
"He's been good, according to our reports from Triple-A," Mattingly said. "He's the guy right now throwing the ball better than anyone else. He's earned this start."
Joe Frisaro has covered the Marlins for MLB.com since 2002. He writes a blog, called The Fish Pond. 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.