JUPITER, Fla. -- Marlins right-hander Jarred Cosart knew something was wrong when he was standing on the mound and home plate seemed like a moving target. Pretty much all of the 2015 season was out of alignment for the 25-year-old.
Cosart dealt with vertigo-like symptoms, and after going through a battery of medical tests, a specialist diagnosed his condition as a right inner ear disorder in August. Through treatment, he feels like his old self again in Spring Training.
• Spring Training:Schedule | Tickets | Complete info
In the mix for the fourth or fifth rotation spot, Cosart faced hitters on Sunday in a live batting practice session at the Roger Dean Stadium complex. Each time on the mound, he's getting sharper.
"I feel great," Cosart said. "I tweaked some mechanical stuff this offseason. I tweaked some grips with [pitching coach] Juan [Nieves] this offseason. All of my bullpens felt really good. My body felt great. I feel I'm in a good spot right now."
No longer does Cosart feel unsteady on the mound, or headachy or dizzy. He has come a long way since last season, a down year in which he finished 2-5 with a 4.52 ERA in 69 2/3 innings.
Still, in the eyes of the team, Cosart has something to prove.
"He's a guy that is fighting for a spot," manager Don Mattingly said. "But he's a guy that has tremendous upside. We think he could be a front-of-the-rotation guy if he can find consistency."
• Koehler to start Grapefruit League opener | Marlins prefer Jackson in rotation 
Last May, Cosart went on the disabled list with vertigo. He was reinstated on June 25, but on July 4 at Wrigley Field against the Cubs, he was rocked for seven runs in 1 2/3 innings.
After the game, the righty was optioned to Triple-A New Orleans, and the balance issues returned. In August, Cosart traveled to Chicago and was treated by a specialist who called his condition an inner ear disorder.
Part of his treatment included doing a series of head movements, as well as following the path of a laser pointer.
"Doing things to get your eyes and ears in tune with each together," Cosart said.

The inner ear disorder, doctors believe, stemmed from a sinus infection developed in May, followed by a long flight to the West Coast and back. The long flight and altitude, it is believed, damaged the nerve in Cosart's ear.
"That is when the vertigo and the ear stuff came in," Cosart said. "From then on, it was kind of downhill, and I came back in September." 
Last September, Cosart was back in the big leagues. He finished strongly, posting a 2.96 ERA in five September starts.
"In general, the whole year last year, I wasn't able to pitch to my full capability," Cosart said. "I think that had a lot to do with it. Anybody can call that an excuse, or whatever. But until you've had it, had vertigo or anything like that, and tried to perform on the mound, in front of 30,000, 40,000 people, you won't know what that's like."