The Marlins announced Fernandez's death, and the U.S. Coast Guard confirmed to the Associated Press that Fernandez was one of three people killed in a boat crash off Miami Beach.
Fernandez was a two-time All-Star who went 38-17 in his four seasons with the Marlins, winning the National League's Rookie of the Year award in 2013. The native of Santa Clara, Cuba became a U.S. citizen last year.
NFL players reacted to news of Fernandez's death on Twitter:
The Associated Press contributed to this report.