2009-10: Miro Aaltonen played 40 games for the Espoo Blues' U20 team as a 16-year-old and was among the top scorers in the U18 SM-Liiga playoffs. He scored 12 goals with 15 assists and was -3 with 18 points in U20 play. He skated for Espoo's U18 team, which reached the bronze medal game, and scored 6 goals with 8 assists in 14 playoff games (sharing the points lead with two other players). Aaltonen represented Finland in the 2010 U17 World Hockey Challenge and had 3 assists and 2 penalty minutes in five games.
2010-11: Aaltonen missed much of the season due to injury but finished with a flourish – skating for the Espoo Blues U20 team that won a silver medal and scoring four goals in six games for Finland at the 2011 U18 World Junior Championship. He scored 3 goals with 5 assists and was +5 with 6 penalty minutes in 12 regular season games and then tallied 5 goals with 6 assists in 13 playoff games, finishing +3 with 2 assists for Espoo's U20 team. Aaltonen played four games for Espoo's U18 team (including two playoff games) and scored 3 goals with 4 assists. He was ranked 69h amongst European skaters in Central Scouting's final rankings prior to the 2011 NHL Draft but was not drafted. He was selected by Atlant Mytischi in the second round (45th overall) of the 2011 KHL Draft.
2011-12: Aaltonen made his pro hockey debut in Finland – skating for the Espoo Blues in the SM-Liiga and with his hometown club of Jokipojat in Mestis (the Finnish second league). He was a key part of Finland's U20 team that reached the bronze medal game at the 2012 World Junior Championship. Aaltonen scored 1 goal with 1 assist and was -2 in limited ice time in 26 games for Espoo during the regular season and in 10 games in the SM-Liiga playoffs he was +2 with 1 goal and 1 assist. In four games with Jokipojat he scored 2 goals with 3 assists and was +3. Aaltonen was a dominant scorer in domestic junior hockey – scoring 12 goals with 20 assists in 18 games (including four playoff contests). Playing on Finland's third line along with Alexander Ruuttu and Aleksander Barkov at the WJC he scored 1 goal with 2 assists and was an even plus/minus in seven games. Aaltonen was ranked 33rd amongst European skaters in Central Scouting's final rankings but was not selected.
2012-13: Aaltonen got off to a fast start for Espoo Blues in his first full SM-Liiga season before suffering a gruesome ankle injury that appeared to be season-ending in Finland's opening game at the 2013 World Junior Championship. He missed the rest of the tournament and the SM-Liiga season but was able to skate for Espoo's silver medal-winning squad in the U20 playoffs. Aaltonen scored 11 goals with 5 assists and was -2 with 22 penalty minutes in 32 SM-Liiga games before joining Finland's U20 team. After scoring 3 goals with 4 assists in eight pre-tournament games for the Finland U20 squad, Aaltonen had 2 goals and an assist in the opening game against Latvia before suffering his injury. Joining the Espoo U20 team in April he scored 4 goals with 9 assists in eight playoff games and was +6 with 4 penalty minutes. Aaltonen was ranked 40th amongst European skaters in Central Scouting's final rankings and was selected by Anaheim in the sixth round (177th overall) in the 2013 NHL Draft.
Aaltonen excels in the offensive part of the game and is noted as a solid puck-possession player with great distribution and creativity. His puck-handling is solid, as well as is his skating. However, he needs to bulk up and work on his defensive play. He does not shy away from physicality but he does not have the frame to consistently deal with it on a nightly basis.
Aaltonen should be considered a low-risk high-reward selection for the Ducks coming in the sixth round of the 2013 draft. Injuries have held up his development on multiple occasions but he still has a promising offensive skill set that could translate to North American hockey. He recently signed an extension with the Espoo Blues of the SM-liiga that will keep him in Finland until at least 2014-15.