 He turned professional in 2001 with the Senators, playing for their minor league affiliate Grand Rapids Griffins of the American Hockey League (AHL) along with some games in the East Coast Hockey League (ECHL) with the Mobile Mysticks.Lajeunesse was called up to the Senators and he played 24 minutes of a March 7, 2002 game with the Senators, stopping all nine shots he faced.But due to a back injury, he couldn't continue the game.