Kammala jumla mai zuwa: Lokacin da Mattsson yake ƙarami, an dauke shi babban tauraro a nan gaba kuma a cikin 1991, yana da shekaru 16 kawai, ya buga Elitserien a kulob din garinsu Malmö IF kuma kafin ya cika shekaru 19, ya lashe gasar Sweden sau biyu (1992 da 1994). A shekarar 1993 Calgary Flames ta zaba shi a matsayin na 18 a cikin
Zaben NHL na shekara ta 1993.