After his second year with HC Košice in which he registered 5 goals and 13 points in 43 games, Černák's promising potential was recognized as he was ranked just outside the top-ten European prospect skaters eligible for the 2015 NHL Entry Draft.

[3] On 14 July 2015, Černák signed a three-year, entry-level contract with the Los Angeles Kings of the National Hockey League.

[6][7] On 19 November, Černák recorded his first NHL point with an assist to Victor Hedman as the Lightning lost 3–2 to the Nashville Predators.

[8] On 2 February 2019, Černák recorded his first career NHL goal against the New York Rangers at Madison Square Garden.

[11] Černák is a cousin of Christián Jaroš, who previously played in the NHL for the Ottawa Senators, San Jose Sharks and New Jersey Devils.