Junior Zadorov played in the 2008
Quebec International Pee-Wee Hockey Tournament with the
HC CSKA Moscow youth team. He played in the top minor hockey level with his hometown team in Moscow, Krasnaya Armiya, in the
2011–12 season. Showing unique agility and skating prowess for a formidable frame, Zadorov scored 6 points in 42 games. He was selected by affiliate
Kontinental Hockey League (KHL) club
CSKA Moscow in the first round, fourth overall, of the
2012 KHL Junior Draft. However, with an impressive performance with the junior national U17 team in
Windsor, Ontario, and stating his intention to pursue a career in North America in order to be selected in the NHL draft,
London Knights general manager Mark Hunter traded up with the
Peterborough Petes in the 2012 CHL Import Draft to select Zadorov ninth overall. After agreeing to a contract with the Knights, Zadorov began his major junior career in the
Ontario Hockey League (OHL) in the
2012–13 season, joining fellow Russian
Vladislav Namestnikov. After adapting to the differing style and dimensions of the North American game, Zadorov assumed a top pairing role and led All-Rookie defencemen in
plus–minus with +33, and finishing second in scoring with 6 goals and 25 points in 63 games. Earning a roster spot in the 2013
CHL Top Prospects Game, Zadorov helped the Knights claim the OHL championship to advance to the
Memorial Cup. Zadorov's impressive season was noted as he was selected with the
Buffalo Sabres's second first-round pick, 16th overall, in the
2013 NHL entry draft.
Buffalo Sabres in 2013. Zadorov attended his first rookie and NHL training camp and after his third pre-season contest he was signed by the Sabres to a three-year, entry-level contract on 26 September 2013. Under the assessment of head coach
Ron Rolston, he made the Sabres' opening night roster to begin the
2013–14 season. Zadorov sat out the first ten games before he made his NHL debut in a 4–2 defeat to the
Colorado Avalanche on 19 October. In just his second game, against the
Boston Bruins on 23 October, Zadorov scored on his first shot in the NHL, against
Chad Johnson. In so doing, he became the youngest Sabres defenceman in franchise history to achieve the feat. With the Sabres cleaning out the front office and coaching staff, and with an imperative to rely less on the youth from new head coach
Ted Nolan, on 19 November, Zadorov was returned to junior with the London Knights after seven NHL games played. He played out the remainder of the season with the Knights, assuming a top-pairing role in surpassing his rookie season totals in points (30) in half the number of games (36), earning a selection to the OHL Second All-Star Team. Despite a benching during the rookie pre-season tournament in
Traverse City, Michigan, Zadorov rebounded to have a strong training camp to make the Sabres' opening-night roster in the
2014–15 season as a permanent addition to the blueline. He initially only saw limited playing time as a rotational option to the third-pairing under Ted Nolan and was primarily on the team for practice only (he was not yet eligible for the
American Hockey League and a tie-up involving Zadorov's KHL rights prevented him from being returned to juniors). Zadorov's playing time soon increased in the season as the team's coaching staff decided to keep Zadorov regardless of his junior situation. In developing a shut-down role through his physicality, Zadorov showed offensive glimpses, collecting his first multi-point game in scoring an overtime marker in a 4–3 victory over the
Florida Panthers on 13 December 2014. Zadorov also became the youngest Sabres defenceman in history to score an overtime winner. Zadorov showed his youth by suffering two team suspensions over the course of his rookie campaign, after returning late from holiday over the All-Star break and later oversleeping through a team practice. Despite a lowly year for the Sabres, Zadorov led the blueline in plus–minus and finished with 3 goals, 12 assists in 60 games.
Colorado Avalanche At the
2015 NHL entry draft, Zadorov was traded as a central piece by the Sabres in a package that also included
Mikhail Grigorenko,
J. T. Compher and the 31st pick in the draft to the
Colorado Avalanche in exchange for
Ryan O'Reilly and
Jamie McGinn on 26 June 2015. Upon learning about the trade, Zadorov said he was happy since he "knew about this organization...it’s always nice to play for a GM who's actually been here and knows what it’s like for the players when you’re playing and working hard." He began the season with the team but was reassigned to their
American Hockey League (AHL) affiliate, the
San Antonio Rampage, in order to improve his game. When speaking of the decision, General Manager
Joe Sakic said "for a young man in that position, he needs to play a ton and work on his confidence. He’ll go down and play as much as he can and keep learning that way. The only way you can get better is by playing a lot at a young man’s age." At the time of his reassignment, he had recorded two assists in 11 games and been a healthy scratch for four consecutive games. Zadorov remained in the AHL until he earned his first recall on 13 January alongside
Chris Bigras after
Nate Guenin was placed on waivers. His stay in the NHL was short-lived, however, as he was reassigned to the Rampage on 23 January after
Erik Johnson was activated from injured reserve. The following year, Zadorov made the Avalanche's lineup out of training camp and remained on their roster for the entirety of the
2016–17 season. In February 2017, Zadorov collided with forward
Mikko Rantanen during practice and suffered a season-ending fractured ankle injury. At the time of the incident, he had recorded 10 assists and no goals in 56 games. Prior to the start of the
2017–18 season, the Avalanche signed him to a two-year contract extension to remain with the team. He was also medically cleared to play but was late returning for the Avalanche's 2017 training camp due to Visa issues. Entering his third season with the team, Zadorov broke one franchise record and set his own new career-high totals in goals, assists, and points. On 22 March, Zadorov surpassed the previous Avalanche record for most hits in a single game with 15, which was also the third-most hits by an NHL player since 1998–99. By the conclusion of the season, Zadorov led the league with 278 hits and recorded a career-best seven goals, 13 assists, and 20 points. On the heels of his most successful season, Zadorov underwent shoulder surgery in the off-season and was expected to miss participating in the Avalanche's 2018 training camp. In spite of this, Zadorov participated in the Avalanche's training camp wearing a non-contact jersey before being cleared as a full participant in practice on 20 September. He ended his fourth year campaign playing in 70 regular season games and recording seven goals, seven assists, and accumulating 75 penalty minutes. As a result, the Avalanche re-signed Zadorov, who was expected to become a restricted free agent, to a one-year, $3.2 million contract. With his newest contract signed, Zadorov returned to the Avalanche for their 2019 training camp, although he left on the third day due to an injury. He was listed as day-to-day with a lower-body injury before fully returning to team practice on 24 September, with fellow injured players
Pierre-Édouard Bellemare and Erik Johnson. During the shortened
2019–20 season, Zadorov suffered a facial fracture as a result of taking a puck to the face during a game against the
Nashville Predators. He returned to the Avalanche's lineup three games later after recovering from surgery to heal his broken jaw. As the Avalanche qualified for the
2020 Stanley Cup playoffs, they faced off against the
Arizona Coyotes in the First Round. They beat the Coyotes in five games and Zadorov recorded his first playoff goal in the 7–1 Game 5 win. During their Second Round contests against the
Dallas Stars, Zadorov passed
Matt Duchene for 74th place on the franchise playoff points list. In the second-round series against the Dallas Stars, despite injuring his arm, Zadorov was able to play through pain, and following the Game 7 defeat to the Stars opted to undergo surgery. He finished the playoffs with 3 goals and 5 points through 15 games. On 8 October 2020, Zadorov as a restricted free agent was tendered a qualifying offer by the Avalanche.
Chicago Blackhawks On 10 October 2020, Zadorov's five-year tenure with the Avalanche ended as he was dealt alongside
Anton Lindholm to the
Chicago Blackhawks in exchange for
Brandon Saad and
Dennis Gilbert. Prior to the trade, he had accepted his one-year, $3.2 million qualifying offer for the
2020–21 season. In his lone season with the Blackhawks, Zadorov appeared in 55 out of 56 regular season games, registering 1 goal and 8 points from the blueline and was unable to help Chicago return to the playoffs.
Calgary Flames of the
Seattle Kraken in 2023. On 28 July 2021, Zadorov – an impending restricted free agent – had his negotiation rights traded to the
Calgary Flames in exchange for a
2022 third-round pick. On 20 August, he agreed to a one-year, $3.75 million contract, avoiding arbitration. On 12 April 2023, Zadorov recorded his first career NHL
hat-trick in a 3–1 win over the
San Jose Sharks. On 10 November 2023, following a loss to the
Toronto Maple Leafs, it was reported that Zadorov had requested a trade.
Vancouver Canucks Zadorov's trade request was granted on 30 November 2023, when he was traded to the
Vancouver Canucks in exchange for a
2024 fifth-round pick and a 2026 third-round pick. He achieved a
Gordie Howe hat trick in a 4–3
overtime loss to the
Colorado Avalanche at
Rogers Arena on 13 March 2024. He earned an
assist on an
Ilya Mikheyev goal in the first period and scored the Canucks' third goal and fought
Josh Manson both in a span of 37 seconds in the second.
Boston Bruins Leaving the Canucks as a free agent having been unable to come to terms on an extension at the conclusion of his contract, Zadorov returned to the Eastern Conference in signing a six-year, $30 million deal with the
Boston Bruins on 1 July 2024. Zadorov brought a big body to the Bruins blue line, hoping to provide physicality alongside top Bruins defenseman
Charlie McAvoy and
Hampus Lindholm. He scored his first points as a Bruin in the second game of the season, with two assists against the
Montreal Canadiens. However, Zadorov was shaky early on the Bruins, as he had only scored five assists through the first twenty games, and had taken on a larger role with Lindholm injured. On November 27, 2024, Zadorov scored his first goal as a Bruin against the
New York Islanders. As the season went on, Zadorov and the Bruins were become increasingly frustrated, as they were slipped out of playoff contention. By the time the trade deadline passed, both McAvoy and Lindholm were out long-term, and the Bruins traded defenseman
Brandon Carlo to the
Toronto Maple Leafs, slotting Zadorov in as the top defenseman on a struggling Bruins team. On March 23, 2025, after a 7-2 loss to the
Los Angeles Kings, Zadorov grew attention after seemingly making a condescending remark towards Bruins goaltender
Jeremy Swayman after Swayman tried to fight Kings goalie
Darcy Kuemper at center ice. In response to a reporter asking if the team appreciated the action from Swayman, sticking up for his teammate, Zadorov responded "Is that what that is? Okay. I don't know. No comment." The comment fueled rumours of locker room discontent in general, as well as towards Swayman in particular. A couple days later, Zadorov clarified the comment, saying that he was frustrated after the loss and that it was not meant as a snub towards Swayman, claiming the media blew it out of proportion. Zadorov and the Bruins would end up missing the playoffs, with Zadorov scoring four goals and 18 assists, tying his career high for assists and points. He also led the NHL with 145 penalty minutes. ==International play==