Mezue ahịrịokwu na-esonụ: Kostitsyn mere ihe ngosi nke abụọ ya n'okpuru 20 na
2002 World Junior Ice Hockey Championship ma gbaa goolu atọ iji nyere Belarus aka ịnọ na ngalaba kachasị elu. Mgbe afọ ahụ gasịrị, Kostitsyn laghachiri na ngalaba kachasị elu na 2002 IIHF World U18 Championship, na-edekọ ihe 10 na egwuregwu asatọ ma na-enyere Belarus aka na njedebe nke ise. Na asọmpi nke atọ ya n'okpuru afọ 20 na 2003 World Junior Ice Hockey Championship, Kostitsyn dekọtara ihe mgbaru ọsọ abụọ na otu enyere aka, mana a chụpụrụ ya na Belarus na Ngalaba-I maka 2004. Na-egwu egwu na nke abụọ, o nwetara ihe mgbaru ọsọ ise na isi iri na ise na egwuregwu ise iji nyere Belarus aka ịlaghachi na nke kachasị elu na 2005, ebe o nwetara isi ise na nke ise ya na nke ikpeazụ World Juniors.