Fernandez was placed on the 15-day disabled list with a sprained right elbow earlier Monday, manager Mike Redmond announced. Fernandez will return to Miami for further evaluation as the Marlins await more results from an MRI in Los Angeles.
A bevy of pitchers have been diagnosed with torn elbow ligaments requiring Tommy John surgery, since the start of spring training. They include Braves right-handers Kris Medlen, Brandon Beachy and Cory Gearrin; Diamondbacks ace Patrick Corbin; Athletics starters Jarrod Parker and A.J. Griffin; Rays All-Star Matt Moore; Yankees starter Ivan Nova; Padres starter Josh Johnson; Mets closer Bobby Parnell; Royals setup man Luke Hochevar; Tigers reliever Bruce Rondon; and top Pirates prospect Jameson Taillon.
"That's probably what everyone is going to talk about and continue to talk about," Redmond said. "We've protected him. We've been consistent in how we've used him, with his workload. We've given him extra days. That's a question I don't think anybody has the answer to."
Fernandez, 21, is 4-2 with a 2.44 ERA in eight starts this season. He leads the majors with 70 strikeouts.
However, he was roughed up during his last outing, Friday against the San Diego Padres, giving up six runs in five innings, including two home runs.
Fernandez's fastball averaged 94.6 mph over his first four innings against the Padres but only 90.7 mph over his last two, according to ESPN's Stats & Information. He allowed four runs in the sixth inning before being removed with nobody out.
"I think you're always concerned when you're talking about elbows," Redmond said. "That's something we have to wait to find out. But I think we're always concerned about that with pitchers, especially."
Last season Fernandez made 28 starts, going 12-6 with a major league-best .182 opponents' batting average. His 2.19 ERA was second in the majors behind three-time defending ERA champ Clayton Kershaw. Fernandez struck out 187 batters and was named NL Rookie of the Year.
The Marlins recalled left-hander Dan Jennings from Triple-A New Orleans. He made 79 relief appearances for the Marlins over the previous three seasons, going 3-5 with a 2.96 ERA.
Information from The Associated Press was used in this report.