Career
He moved to Sweden in 2009 with Leksands IF of the HockeyAllsvenskan before joining Elitserien club, Djurgårdens IF the following season on May 31, 2010. After a season stint in the EBEL with Austrian club, Graz 99ers, Lassen moved to Finland signing a two-year contract with the Lahti Pelicans of the Liiga on March 27, 2015. He also participated in two IIHF World Championships before joining Leksands IF in May 2009.
Lassen was named for the Danish team again in the 2010 IIHF World Championship.
He scored the game-winning goal against United States of America in the preliminary round.
