Demers was one of three rookies who carved out a small piece of history in the second game of his NHL career while playing for the San Jose Sharks. On Oct. 3, 2009, Demers and Frazer McLaren set up Benn Ferriero for a goal, as each got his first NHL point in a 4-1 victory against the Anaheim Ducks.

Demers has gone on to establish himself as a reliable defenseman who can move the puck quickly and efficiently and doesn't hesitate to join the rush and contribute offensively.

A native of Dorval, Quebec, Demers broke out as an NHL prospect when he scored 64 points in 67 games for Victoriaville of the Quebec Major Junior Hockey League during the 2007-08 season. He was drafted by the Sharks in the seventh round (No. 186) of the 2008 NHL Draft and began his pro career with Worcester of the American Hockey League a year later.

After having 33 points (two goals) in 78 games, Demers had four more points (all assists) in 12 AHL playoff games, which began a six-year run in which he participated in the postseason. The last five of those appearances were with the Sharks.

On Nov. 21, 2014, the Sharks traded Demers to the Dallas Stars. He had 12 goals and 45 points in 123 games with the Stars before signing a five-year, $22.5 million contract with the Florida Panthers on July 2, 2016.