Manson became a defenceman during his second season with the Silverbacks, following injuries to the lineup and elected to develop himself in the position.[5]
Manson recorded 12 goals and 35 assists in 57 games with the Silverbacks, which earned him consideration to be selected in the 2011 NHL Entry Draft.[4] Prior to the 2011 NHL Entry Draft, Manson accepted a scholarship to play NCAA Division I ice hockey for Quinnipiac University for the 2012–13 season.[6] Manson was drafted in the sixth round, by the Anaheim Ducks.[7] Following his selection, Manson opted to transfer from Quinnipiac to Northeastern University.[4]
On March 25, 2014, forgoing his final year of collegiate eligibility, Manson signed a two-year, entry-level contract with the Anaheim Ducks.[13] He began the season with the Norfolk Admirals in the American Hockey League (AHL) before being recalled to the NHL level due to various injuries. After Mark Fistric suffered an upper-body injury during a game against the St. Louis Blues he subsequently made his NHL debut on October 31, 2014, against the Dallas Stars. During the game, he registered one hit in 12:30 of ice time and played on the teams' penalty kill.[14] Manson split his time between the Admirals and Ducks during the season, playing 28 games with Anaheim and 36 games in the AHL.[15]
After attending the Ducks' training camp, Manson was named to their opening night roster prior to the 2015–16 season but was shortly thereafter placed on their injured reserve due to an unspecified upper-body injury.[16] Following a game against the Toronto Maple Leafs on March 24, Manson was fined $2,487 for making an inappropriate throat-slashing gesture towards Nazem Kadri.[17] As the Ducks made the 2016 Stanley Cup playoffs, Manson played in Game 1 of the First Round against the Nashville Predators but was knocked out of the game following a hit from Filip Forsberg.[18] As a result of the hit, Manson did not play for the remainder of the series.[19]
The following season, Manson scored his first career NHL goal on November 6 during a home game against the Columbus Blue Jackets. He scored at 8:46 of the third period to help the Ducks win 4–2.[20] He appeared in 71 games and recorded 15 points while playing alongside Hampus Lindholm.[15] During the Ducks' playoff berth, Manson was praised for his physical play during their series against the Edmonton Oilers and Nashville Predators. In Game 7 against the Oilers, Manson set a new franchise playoff hit record with 11 within 20:38 of ice time in the 2–1 win.[21]
On October 4, 2017, Manson signed a four-year contract extension with the Ducks through the 2021–22 NHL season.[22] In the first year of his new contract, Manson set career highs in goals, assists, and points.[15] He continued to play alongside Lindholm and they combined for a 53.53 Corsi-For percentage at even strength.[23]
After attending the Ducks' training camp, Manson was named to their opening night roster prior to the 2019–20 season. However, in late October Manson suffered an MCL sprain during a game against the Dallas Stars and was expected to be out of the lineup for 5–10 weeks.[24]
In the following pandemic shortened 2020–21 season, on January 21, 2021, it was announced that Manson would be out nearly six weeks with an oblique muscle injury sustained against the Minnesota Wild.[25] He was limited to just 23 regular season games, posting 7 points, as the Ducks missed the post-season for the third consecutive year.
In his seventh season with the Ducks in 2021–22, Manson as the veteran and alternate captain on the blueline for the rebuilding Ducks, contributed with 4 goals and 9 points through 45 games.
Colorado Avalanche
While in the final season of his four-year contract and with the Ducks trending out of playoff contention, Manson was traded to the Colorado Avalanche, in exchange for Drew Helleson and a 2023 second-round draft pick on March 14, 2022. He ended his tenure with Anaheim, placing fifth all-time among franchise defenseman in games played with 453.[26] He made his debut with the Avalanche against the Los Angeles Kings, demonstrating his physical presence to register a game high 10 hits, in a 3–0 victory on March 15, 2022.[27] On May 17, 2022, Manson scored his first career playoff goal, an overtime winner against the St. Louis Blues.