[1] Jeník was selected by the Flint Firebirds of the Ontario Hockey League (OHL) in the first round, sixth overall of the 2018 CHL import draft.
[4] He returned to North America and was assigned to Arizona's American Hockey League (AHL) affiliate, the Tucson Roadrunners for the 2020–21 season.
He was recalled by Arizona for the final two games of the season in May 2021[5] and made his NHL debut versus the San Jose Sharks on 7 May 2021.
A restricted free agent following the season, he signed a one-year, two-way contract with Arizona on 20 September 2023.
[15] He cleared waivers and was assigned to Ottawa's AHL affiliate, the Belleville Senators, to start the 2024–25 season.