A defenseman-turned-forward in high school, Gilbert returned to defense in college but retained his offensive instincts as a mobile puck-mover. At 6-foot-2 and 202 pounds, he has provided a physical presence in his own zone during a long NHL career.

The Bloomington, Minn., native was selected by the Colorado Avalanche in the fourth round (No. 129) in the 2002 NHL Draft and traded to the Edmonton Oilers for Tommy Salo and a 2005 sixth-round draft pick on March 8, 2004. Gilbert made his NHL debut with the Oilers against the San Jose Sharks on Jan. 10, 2007. His first NHL goal (and point) on Feb. 20, 2007, against the Ottawa Senators forced overtime with 20 seconds left of a 4-3 shootout loss, and he finished the 2006-07 season with a goal and six points in 12 games.

Gilbert began 2007-08 with the Oilers and scored his first goal of the season in Edmonton's season opener, a 3-2 win against San Jose on Oct. 4, 2007. He set franchise records for goals (13) and points (33) by a rookie defenseman and finished second in the League in scoring among first-year players at the position. He led NHL rookies and was 11th in the NHL with 159 blocked shots. Gilbert made the NHL All-Rookie team and became the first rookie to be named Edmonton's Defenseman of the Year.

Gilbert, who did not miss a game over his first three full NHL seasons, saw his consecutive-games streak end at 332 because of a back injury late in the 2010-11 season. During that streak he finished 10th among NHL defensemen with 40 assists in 2008-09 and 10th in the NHL with 165 blocked shots in 2009-10. Edmonton traded Gilbert to the Minnesota Wild for Nick Schultz on Feb. 27, 2012, and he made his Stanley Cup Playoff debut in 2013, appearing in all five games of the Wild's first-round series with the Chicago Blackhawks.

After spending 2013-14 with the Florida Panthers, Gilbert signed as a free agent with the Montreal Canadiens on July 1, 2014. He led the Canadiens with 33 blocks during the 2015 playoffs.

A knee injury in February ended Gilbert's 2015-16 season. He signed a one-year, free agent contract with the Los Angeles Kings on July 1, 2016.

Before entering the NHL, Gilbert played for the University of Wisconsin for four seasons. The Badgers' MVP in 2004-05 and an assistant captain for his junior and senior seasons, Gilbert scored the winning goal in Wisconsin's 2-1 victory over Boston College in the 2006 NCAA championship game.