A highly decorated player in junior hockey, Carlson made a name for himself before turning pro.

The strong two-way defenseman started his path to the NHL with Indiana of the United States Hockey League. He was named to the league's All-Rookie Team and was a Second Team All-Star in 2007-08 after finishing with 12 goals and 43 points in 59 games.

After Carlson was selected by the Washington Capitals in the first round (No. 27) of the 2008 NHL Draft, he bypassed college and signed with London of the Ontario Hockey League. In his only season there, Carlson was an OHL Second Team All-Star and was named team MVP for London after he had 16 goals and 76 points in 59 games. Carlson added seven goals and 22 points in 14 postseason games as London advanced to the third round in the OHL playoffs.

Following London's elimination, Carlson joined Hershey for the American Hockey League playoffs, appearing in 16 postseason games and helping the Bears win the Calder Cup.

Carlson made his NHL debut on Nov. 20, 2009, part of a three-game stint with the Capitals. As a member of the United States World Junior Championship team in 2010, Carlson secured a gold medal for his country when he scored the overtime winner against Canada in the championship game, his second goal of the game. He was named to the all-tournament team.

Carlson was called back up to Washington for the final month of the season and scored his first NHL goal on March 25, 2010, against the Carolina Hurricanes. He then got his first Stanley Cup Playoff goal in Game 2 of a first-round series loss to the Montreal Canadiens.

He would rejoin Hershey for the AHL playoffs, where he starred again, scoring the Calder Cup-clinching goal. Carlson earned a full-time spot with the Capitals for the 2010-11 season. He was named to the NHL All-Rookie Team and finished fifth in voting for the Calder Trophy, awarded to the top rookie in the NHL, after scoring seven goals and 37 points in 82 games.

Carlson has continued to stand out, producing on offense and serving as a shutdown defenseman, using his exceptional mobility and size (6-foot-3, 215 pounds) in the defensive zone.