Marlins' Fernandez to have Tommy John surgery

San Francisco, CA ( - Miami Marlins pitcher Jose Fernandez has decided to undergo Tommy John surgery.

Fernandez endured a rough outing in San Diego on May 9, as he was tagged for six runs -- five earned -- in five innings and saw a noticeable decrease in velocity on his fastball towards the end of his start.

After he was diagnosed with a tear in his ulnar collateral ligament, the team doctor recommended the season-ending surgery.

Fernandez, who was placed on the 15-day disabled list Monday, decided to have Tommy John surgery after speaking with his family.

"To all my fans: you deserve to know that today, along with my family, I made The decision to undergo tommy john surgery," Fernandez wrote on his Instagram account Thursday. "It was not an easy one, but with my condition it is the only option where I can return to the game I love as the same player I am temporarily leaving the game as. I'll be back as soon as my elbow will let me . And if anything... I have about a year to learn how to throw lefty ;)You haven't seen the last of me Miami, I promise you that."

Fernandez, the reigning National League Rookie of the Year, was 4-2 with a 2.44 earned run average over eight starts before the injury.

The 21-year-old right-hander will be sidelined for at least 12 months. The surgery will take place on Friday in Los Angeles.