Prior to being drafted by the Thrashers, Štefan played for Sparta Praha in the Czech Republic, and the Long Beach Ice Dogs of the IHL.

On 24 June 2006, Štefan was traded to the Dallas Stars along with Jaroslav Modrý for Niko Kapanen and a seventh-round draft pick in 2006.

With seconds left in the game, and Dallas already ahead by a goal, Štefan gained possession of the puck and found himself on a breakaway towards an empty net.

Štefan continued skating towards the crease rather than immediately shooting, then attempted a casual backhand into the net from close quarters.

This allowed a play to develop where fellow Czech Aleš Hemský scored with two seconds remaining to tie the game 5–5; ultimately, Dallas won in a shootout.