Career
Hainsey was drafted in the first round, 13th overall by the Montreal Canadiens in the 2000 National Hockey League Entry Draft, from collegiate team the University of Massachusetts Lowell. He started his professional career with AHL teams, Quebec Citadelles and the Hamilton Bulldogs. After spending three seasons in the Canadiens organization was claimed off of waivers on November 29, 2005, by the Columbus Blue Jackets, where he established himself into a leading two-way defenseman.
On July 2, 2008, the Atlanta Thrashers signed Hainsey to a five-year, $22.5 million contract.
He scored six goals to go along with 33 assists in his first season in Atlanta. He would go on to record 45 points in the next two seasons with the Thrashers.
Upon their move to Winnipeg to start the 2011-2012 National Hockey League season, Hainsey recorded 10 assists in 56 games for the Jets in 2011-2012. Hainsey also played a role in the negotiations of the 2012 National Hockey League lockout.
After a day of marathon bargaining sessions on December 5, 2012, Hainsey emerged to tell the media that both sides planned to meet again the next day.
On September 12, 2013, Hainsey signed a one-year, $2 million contract with the Carolina Hurricanes after the team announced defenseman Joni Pitkanen would miss the season due to injury.