After his draft selection, he would spend two seasons in the junior Western Hockey League with the Edmonton Oil Kings before signing a three-year entry-level contract with the Oilers on April 20, 2013.

[1] He spent the next three seasons playing in the American Hockey League for the Oklahoma City Barons and the Bakersfield Condors before he was traded to the Anaheim Ducks on February 29, 2016 for Patrick Maroon.

[2] He would play just five games for the Ducks' AHL affiliate the San Diego Gulls before signing for HC Sparta Praha for the 2016–17 season.

On 7 June 2023, Gernát signed as a free agent to a one-year contract with Russian club, Lokomotiv Yaroslavl of the KHL, for the 2023–24 season.

[4] Gernát was selected to play for Slovakia at the 2012 World Junior Championships.