When Carlson was traded to the Anaheim Ducks by the Washington Capitals on March 5, 2026, he left as the Capitals' all-time leader among defensemen in goals (166), assists (605), points (771), power-play points (273) and games played (1,143).

Carlson, a strong, two-way skater, was a key to the Capitals' run to their first Stanley Cup championship in 2018.

After finishing the 2017-18 regular season with NHL career highs in goals (15), assists (53) and points (68), Carlson was even better during the postseason. He led all defensemen in the playoffs with 20 points (five goals, 15 assists) and had a plus-11 rating in 24 games.

The Capitals locked up Carlson long term on June 24, 2018, signing him to an eight-year, $64 million contract, and he responded with 70 points (13 goals, 57 assists). Carlson was even better in 2019-20, finishing with 75 points (15 goals, 60 assists), tops among NHL defensemen, and earning his second straight trip to the NHL All-Star Game.

But Carlson made a name for himself even before turning pro.

His journey to the NHL started with Indiana of the United States Hockey League. He was named to the USHL's All-Rookie Team and was a Second Team All-Star in 2007-08 after finishing with 43 points (12 goals, 31 assists) in 59 games.

After Carlson was selected by the Capitals with the No. 27 pick of the 2008 NHL Draft, he bypassed college to play for 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 76 points (16 goals, 60 assists) in 59 games. Carlson had 22 points (seven goals, 15 assists) in 14 postseason games to help London advance 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, during a three-game call-up by the Capitals. As a member of the United States team at the 2010 IIHF World Junior Championship, Carlson scored the gold medal-winning goal in overtime against Canada in the championship game, his second goal of the game, and was named to the all-tournament team.

After Carlson was recalled by Washington for the final month of the season, he scored his first NHL goal on March 25, 2010, against the Carolina Hurricanes. He scored his first Stanley Cup Playoff goal in Game 2 of a first-round loss to the Montreal Canadiens. After the Capitals were eliminated, he rejoined Hershey for the AHL playoffs and scored the Calder Cup-clinching goal.

He earned a full-time spot with the Capitals in 2010-11, was named to the NHL All-Rookie Team and finished fifth in voting for the Calder Trophy after finishing with 37 points (seven goals, 30 assists) in 82 games.

Carlson continued to stand out, producing on offense and using his exceptional mobility and size (6-foot-3, 218 pounds) in the defensive zone. He's also durable: 2017-18 was the fifth time in his NHL career that he played all 82 regular-season games.

Carlson was a runner-up to Roman Josi of the Nashville Predators for the 2020 Norris Trophy given to the best defenseman in the NHL after he had 75 points (15 goals, 60 assists) in 69 games before the regular season was paused due to concerns surrounding the coronavirus. He became the first Capitals defenseman and 11th born in the United States to reach 600 NHL points in a 5-1 win against the Tampa Bay Lightning on Nov. 11, 2022, passing Michal Pivonka (599) for the fifth-most points in team history.

Carlson scored in his 1,000th NHL game for the Capitals, a 3-2 shootout loss to the Boston Bruins at Capital One Arena on March 30, 2024. He scored his 150th NHL goal and passed Kevin Hatcher for the most goals by a defenseman in Capitals history during a 4-2 win against the Lightning at Capital One Arena on April 13.

Carlson became the seventh United States-born defenseman in NHL history to reach 700 points with an assist in Washington's 4-3 shootout loss at the Buffalo Sabres on Jan. 6, 2025. He achieved the milestone in his 1,049th NHL game, the 25th at his position to do so in fewer than 1,050 games.