Marc Denis was a standout goaltender with the local Montreal-Bourassa and Trois-Rivieres entries in the Quebec Midget AAA Hockey League. He then starred for three years with the QMJHL's Chicoutimi Sagueneens and helped the squad reach the Memorial Cup tournament in 1997. The talented youngster was taken 25th overall by the Colorado Avalanche in 1995 NHL Entry Draft.
Denis backed up Montreal Canadiens netminder Jose Theodore when Canada won gold at the 1996 World Junior Championship then was named the top goaltender at the 1997 tournament after leading his country to gold the following year. Denis was named the top goaltender in the QMJHL and CHL and was a First Team QMJHL and CHL All-Star in 1997.
The young backstopper spent most of his first two pro seasons with Colorado's AHL affiliate in Hershey. In 99-2000 he recorded three shutouts and a 2.54 GAA as Patrick Roy's understudy in Colorado. In the off-season he was traded to the expansion Columbus Blue Jackets and posted a respectable 3.25 goals against mark on the over-matched first year club.
Since his arrival with the Blue Jackets, Denis has been a work horse for the Blue Jackets establishing an NHL record for minutes played in 2002-03 with 4,510 minutes and a career high 27 wins.
After five seasons with the Blue Jackets Denis was traded to the Tampa Bay Lightning for forward Fredrik Modin and goaltender Fredrik Norrena.
Aside from his two appearances at the World Junior Championships, Denis was a member of Canada's gold medal winning team at the 2004 World Championships.