Niemelä, 23, was a third-round pick by the Maple Leafs in 2020 and quickly became one of the organizations most promising prospects with a strong season as a teenager in the SM-Liiga in Finland with Karpat. Niemelä became a top-ranking name in the Leafs system at the 2021 World Juniors when he was named top defenceman at the tournament with eight points in seven games as Finland went on to win the bronze medal.