"I haven't heard that yet, but I'm sure he's going to start throwing [soon]," Marlins manager Don Mattingly said. "If he sits too long without throwing, that's going to make the process longer. I'm thinking in the near future he's going to start throwing."
The club is confident that Chen will miss about a month, and that pitching in September is realistic. He recently had a cortisone shot to his elbow to relieve discomfort and inflammation.
The left-hander, who is 5-4 with a 4.99 ERA, has thrown 110 innings, striking out 89.
Even before Chen's injury, the Marlins were searching for starting pitching depth. They acquired a pair of right-handers from the Padres on Friday in Rea and Cashner. Rea made his Miami debut on Saturday against the Cardinals, and Cashner is scheduled to start Sunday.
To make room in the rotation, the Marlins on Saturday optioned Jose Urena -- who took an 11-6 loss to St. Louis on Friday night -- to Triple-A New Orleans. Miami also recalled right-handed reliever Brian Ellington to provide more bullpen depth.
If Chen is available in the final month, Miami will be getting back an experienced lefty for the stretch run.
"He's doing strengthening exercises, things like that," Mattingly said. "He seems to be OK. He won't be on the trip with us [next week], but he is in the process of starting to do some things now."
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.