He played in Major League Baseball (MLB) for the Kansas City Royals, Florida Marlins, and Tampa Bay Rays.

At age 17, Oviedo assumed the identity of his 16-year-old best friend, Leo Nunez, in order to receive a more lucrative contract.

In 2011, Marlins reliever Edward Mujica, a close friend of Oviedo's, said that "[a]t 17 years old, you maybe lose $100,000 or $150,000 when you sign [compared to a 16-year-old with the same skills].

Along with teammates Ambiorix Burgos and Andrew Sisco, they were the first trio of rookie pitchers in major league history to throw at least 50.0 innings each without making a start.

In 2006, Oviedo played for the Double-A Wranglers, Triple-A Omaha Royals, and at the major league level.

[7] During a triple-A rehab game on July 16, Oviedo sprained his right elbow's ulnar collateral ligament[8] and was later placed on disabled list.

After missing all of the 2013 season, Oviedo had his $2 million club option for 2014 declined, and was instead paid a $30,000 buyout, making him a free agent.

[14] The Associated Press reported that his real name was Juan Carlos Oviedo, that he was a year older than listed, and that he returned to the Dominican Republic to deal with the issue.

[15][16] Dominican Central Electoral Commission President Roberto Rosario said that Oviedo signed a sworn statement saying he used fake identification documents.