Complex sentence: He spent three seasons with their AHL affiliate the Philadelphia Phantoms before he was traded to the Atlanta Thrashers where he made his National Hockey League debut with the Thrashers during the 2001--02 season.
Split into simpler sentences: He spent three seasons with their AHL affiliate the Philadelphia Phantoms before he was traded to the Atlanta Thrashers. With the Thrashers, Lessard made his National Hockey League debut with the Thrashers during the 2001--02 season.