After recording 25 points over 50 games in 2011–12 with Nomad, Barys decided to receive rights to him selecting 121st overall in the fourth round of the 2012 KHL Junior Draft.

Later, he scored his first KHL goal, a game winner against Jakub Kovar in a 4–1 win against the Avtomobilist Yekaterinburg on January 10.

[10] Mikhailis made his international debut with Kazakhstan in Division IB of the 2012 IIHF World U18 Championships, held in Hungary.

He scored 1 goal and 3 assist in 5 matches as Kazakhstan finished second in their group to Poland, missing out on a promotion to the main tournament for the following year.

[15] In December 2013, Mikhailis made his second appearance at the under-20 level in the 2014 IIHF World Junior Championships' Division I tournament, held in Great Britain.

[16] At his third appearance for the under-20 team at the 2015 IIHF World Junior Championships, held in Hungary, Mikhailis helped Kazakhstan to promote to Division IA and became tournament's top scorer with 11 points.