2008-09: Joel Armia spent most of the season with Assat's Under-16 Junior “C” team. In 27 games, he scored 36 goals and added 19 assists for 55 points along with 92 penalty minutes. In 3 playoff games for that team, Armia scored 3 goals and added 1 assist for 4 points to go along with 22 penalty minutes. Armia also played for Assat's Under-18 Junior “B” team, scoring 3 goals and adding 1 assist in 6 games. In 10 international games for Finland's Under-16 squad, Armia scored 1 goal and added 2 assists for 3 points.
2009-10: Played most of the season with Assat's Under-20 Junior “A” team. In 27 games for that team, Armia scored 15 goals and added 6 assists for 21 points. In 5 playoff games for that team, Armia scored 1 goal and added 1 assist for 2 points. Armia also played for Assat's Under-18 Junior “B” team, scoring 7 goals and 9 assists for 16 points in 9 games. He also tacked on 31 penalty minutes in those games. In 6 playoff games for that squad, Armia scored 6 goals and added 3 assists for 9 points. Armia played for Finland at the 2010 World Under-17 Hockey Challege, scoring 5 goals and chipping in 3 assists for 8 points in 5 games. His performance earned him a berth on that tournament's All-Star Team. Armia also played in international tournaments with Finland's Under-18 squad, scoring 2 goals and adding 1 assist for 3 points in 5 games.
2010-11: Armia spent most of the season with Assat's top team, playing in 48 games for that club. He scored 18 goals and added 11 assists for 29 points. In 5 playoff games, Armia scored 2 goals for Assat. Armia played for Finland at the 2011 Under-20 World Junior Championship, picking up 1 assist in 6 games. He also played for Finalnd's entry at the 2011 Under-18 World Junior Championship, where he scored 4 goals and added 9 assists for 13 points in 6 games.
2011-12: Armia was Assat Pori's third-leading scorer as an 18-year-old and represented Finland in the 2012 U20 World Junior Championship. He scored 18 goals with 20 assists and was plus-12 with 64 penalty minutes in 54 SM-Liiga games for Assat. Armia appeared in just three playoff games, suffering a season-ending knee injury, and was minus-one with 2 assists. Playing on Finland's second line along with Joonas Donskoi and Miikko Salomaki (NSH) at the WJC, he had 5 goals with 2 assists and was plus-two with 16 penalty minutes in seven games. Finland finished fourth in the tournament; falling to eventual champion Sweden in a shootout in the semifinals. Armia was the only Finnish player to score in the shootout.
2012-13: Armia signed a three-year entry level contract with the Sabres in June of 2012 before returning to Assat Pori for his third SM-Liiga season. He also represented Finland in the 2013 World Junior Championship. He was the second-leading goal scorer for Assat, with 19 goals in 47 games and had 14 assists while finishing +12 with 32 penalty minutes. Assat Pori captured the SM-Liiga's Kanada Cup championship after finishing fourth in the regular season.Armia scored 3 goals with 5 assists and was +4 with 20 penalty minutes in 16 playoff games. Skating for Finland's U20 team for the third time, he scored 6 goals with 6 assists and had 12 penalty minutes in six games at the WJC.
A budding power forward, Armia is one of Finland’s most heralded young players. He has a rare combination of size and goal-scoring ability, using his 6’3 to shield the puck and soft hands to stickhandle and shoot. He needs to work on his defensive play, especially 1-on-1, and his skating ability.
Armia is a significant piece of Buffalo’s youth movement. He will get a good chance to crack the Sabres lineup in a top six role, but if he is not ready the Sabres are not averse to sending their top prospects to the AHL.