In December of his draft year, the 2023–24 season, Jiříček suffered a season-ending knee injury during an international competition.
[3] His lackluster point production in the Extraliga and uncertainty related to his injury tempered expectations for Jiříček, and the consensus entering the draft was that he would be picked in the late first round.
He reunited with fellow defenceman Tomáš Hamara, who Jiříček played with during the 2024 World Junior Championships.
[7] As an alternate captain representing the Czech Republic under-18 at the 2022 World U-17 Hockey Challenge, Jiříček recorded a goal and an assist in six games.
He suffered a knee injury in the opening match against Slovakia junior team, for which he underwent surgery and was replaced by Adam Židlický.