Hirvonen, 19, enjoyed a strong showing at last year's tournament, scoring twice and adding 4 assists for 6 points in 7 games for the Fins, who went on to win the bronze medal.
Niemela, also 19, won the tournament's defensive MVP award last year, but was limited to just 15 games with Karpat in the SM-liiga last season, due to injury.
After being limited to just 4 assists in 15 games last year, Niemela has been absolutely on fire for Karpat this season, leading all defensemen in the league in scoring and is on a historic pace with 24 points in 31 games.