The Marlins have not yet decided how Cosart will be used, but manager Dan Jennings didn't rule out the right-hander starting on Sunday against the Mets. Urena, on the DL with a left knee contusion, will start off in the bullpen, Jennings said.
Cosart, who opened the season in the rotation, was optioned to New Orleans on July 4, and while in the Minor Leagues, he went on the disabled list due to an right inner ear disorder.
In May, he was hampered by vertigo. But after seeing a specialist in early August, he was diagnosed with an inner ear disorder, which affected his balance and gravity.
"Dizziness, nausea, everything you could imagine about being off-balanced," Cosart said about his condition. "It was terrible."
Cosart believes he dealt with the vertigo all season. The 25-year-old has made nine big league appearances, with eight starts, and he's 1-4 with a 5.36 ERA.
"I feel good," Cosart said. "I'm built up. I'm able to throw 100 pitches now. We'll see what happens.
"I'm just happy to be healthy. Whatever they want me to do. I don't think this is something that is going to make or break anything moving forward. Obviously, I'd like to have a good last month, whatever my role is, whatever my job is."
Solano adds infield depth, which Miami needs now that shortstop Adeiny Hechavarria is missing a few games with a tight left hamstring, which he felt on Wednesday at Atlanta.
Hechavarria may miss this weekend's series vs. the Mets. Miguel Rojas started at shortstop on Friday.
As for the pitching, Jennings and pitching coach Chuck Hernandez are monitoring innings, especially of their rookies such as Adam Conley and Justin Nicolino.
"As we go into the remaining portion of this month, Chuck and I have talked about if some of these guys are reaching a high threshold in innings, we could piggyback some of them," Jennings said.