The Marlins reliever had an MRI exam in Miami by team physicians, who determined the right-hander has a sprained right ulnar collateral ligament. There is no timetable for his return.
The injury occurred while Oviedo was pitching on a rehab assignment with Triple-A New Orleans. The right-hander left Saturday's game in the seventh inning after feeling some discomfort in his right elbow.
The 30-year-old is serving an eight-week suspension for playing under a false identity. Formerly known as Leo Nuñez, Oviedo has been preparing to return to the big leagues. He began his rehab assignment on July 9 with Class A Jupiter. His first appearance with New Orleans was cut short by the elbow discomfort.
Prior to learning the results of Oviedo's MRI, Marlins manager Ozzie Guillen hoped the 30-year-old was just experiencing "Spring Training fatigue." But now Guillen knows that Oviedo will have another obstacle to overcome before he can pitch again this season.
"I hope it's nothing bad," Guillen said. "This kid went through [a lot] for the last year, and if something happens to his arm, that's very sad. I think about him first and the team later. This kid has gone through a lot of bad stuff in order to come back."
Oviedo, who saved a career-high 36 games in 2011, is eligible to return to the Majors on July 23, but his UCL sprain will likely delay his arrival. Once he rejoins the big league club, he will join Heath Bell and Steve Cishek as late-inning options.