Career
Classen played college hockey at Merrimack College and went undrafted. He spent his first five pro seasons in the Nashville Predators organization, splitting time between the parent club and the Milwaukee Admirals. In 2004 Classen signed with Finland"s Master of Science-liiga club Ässät.
Returning to the Admirals for 2005-2006, he played the following season in Germany with DEL club, the Hamburg Freezers.
On July 3, 2007, it was announced he had signed a contract with the Vancouver Canucks. He was then reassigned by the Canucks, and played with their American Hockey League affiliate, the Manitoba Moose.
He moved to fellow AHL team Providence Bruins the following season and after 1 game moved onto the San Antonio Rampage before leaving for German team, Iserlohn Roosters, where he spent the remainder of the 2008-2009 campaign. He started the 2009-2010 season with the Rapperswil-Jona Lakers of the Swiss top flight, before transferring to second-division side EHC Basel Sharks during the season.
In January 2010, he moved on to another Swiss team, The Human Context Sierre-Anniviers.
On July 18, 2010, Classen returned to the German DEL and signed a two-year contract with Kölner Haie. After three seasons with Haie, Classen left as a free agent to sign with European Research Council Ingolstadt. In 2014, he joined German second-division side Lausitzer Füchse on a two-year deal.
On March 14, 2015, he was attacked with a knife and severely injured.
He was hospitalized for almost a month and returned to game action in September 2015.