After Lašák was drafted by the Predators, he moved to North America and spent his first professional season with the Hampton Roads Admirals of the East Coast Hockey League (ECHL).

However, he was unable to earn a permanent spot with the Predators, appearing in only 6 games for the team, and posting an 0-4 record.

Due to his inability to stick with the Predators, Lašák decided to return to Europe and spent the 2003-04 season with SKA St. Petersburg of the Russian Super League.

Following his successful stint in the Czech Extraliga, Lašák spent the 2009-10 season with Atlant Mytishchi of the Kontinental Hockey League.

He also spent part of the season on loan to HC Košice of the Slovak Extraliga, appearing in 17 games for the club.