2011-12: Miro Karjalainen skated for the Espoo Blues second team at the U16 level. In 23 games he had 7 assists and 57 penalty minutes.
2012-13: Karjalainen played for the lower division club EKS in Espoo — skating in two game’s with the club’s Division III men’s team — and appeared in two games with the Kiekko-Vantaa U18 team in the top division. He had no points nor penalties playing for the EKS men’s team nor with Kiekko-Vantaa. In four games with the top EKS U18 team he scored 4 goals with 2 assists and 2 penalty minutes.
2013-14: Karjalainen went from Espoo to Helsinki to skate for the Jokerit U18 team and was a steady force on the blueline as the team captured the B juniors national title. He scored 1 goal with 7 assists and had 57 penalty minutes in 38 regular season games and in 11 playoff games scored 2 goals with 3 assists and 6 penalty minutes. Karjalainen was ranked 139th amongst the 140 international skaters in the Central Scouting final rankings and was selected by Dallas in the fifth round (135th overall) of the 2014 NHL Draft.
2014-15: Karjalainen missed most of the season due to injury and illness. He played 10 regular season games with the HIFK Helsinki U20 team, finishing -7 with 1 assist and 8 penalty minutes. Karjalainen scored 2 goals with no penalties and was -1 in three games in the A Juniors playoffs.
Karjalainen is a bit raw as a prospect but has the physical tools and attitude to one day be a strong shut-down defender. He is a big player who is physically imposing and likes to play an aggressive physical game.
Karjalainen made his Liiga debut in two games with the HIFK Helsinki men's team in December but has struggled to stay healthy once again in 2015-16. Spending most of the year with the HIFK U20 team, Karlainen's inactivity has hampered his development. His size and determination suggest he has the potential to be an effective defender but to this point he remains fairly raw in terms of being a prospect.