He joined the Ottawa Rough Riders in the 1981 CFL season as a centre and played all five years of his professional career for the Riders.
1981 | the season | 2005 NFL season | 1995 AFL season | season | 2005 World Touring Car Championship season | 1994 NFL season | 1981 in music | 2013–14 figure skating season | 2012 NFL season | 2009 NFL season | 2010 NFL season | 2006 NFL season | 2013–14 NCAA Division I men's basketball season | 2006 Formula One season | 2005 Atlantic hurricane season | 1981 in film | 1972–73 WHA season | Ontario general election, 1981 | 2013 NCAA Division I FBS football season | 2012–13 figure skating season | 2011 NCAA Division I FBS football season | 2008 NFL season | 2013 CFL season | 2012–13 NCAA Division I men's basketball season | 2009 World Touring Car Championship season | 2007 CFL season | 2003 NFL season | 1996–97 WCHL season | 1960 Philadelphia Eagles season |
Eight games into the 1981 CFL season, head coach Vic Rapp saw Klassen's potential on the defensive side of the ball and he switched him to defensive tackle after defensive lineman Rick Goltz suffered a season-ending injury.