Tomás began his professional career in his home country, Cuba, where he played for the Industriales de La Habana in the Cuban National Series League.

His first professional year of baseball was in 2008 where he played 35 games batting .297 with a home run, four stolen bases, and 11 RBI.

He was called up to the majors on April 15 and made his MLB debut that day, grounding out in his lone at-bat.

[12] On April 2, 2019, Tomás cleared waivers and was outrighted from the Diamondbacks 40-man roster, remaining with the Triple-A Reno Aces.

On May 20, 2019, while in Triple-A, Tomás hit four home runs in a single game as the Aces beat the Tacoma Rainiers 25–8.

[20] In January 2018, Tomás was arrested for criminal speeding when he was allegedly driving 105 miles per hour (169 km/h) on Arizona State Route 101.