[5] Having played alongside Vancouver Canucks prospect Cody Hodgson, who had been selected tenth overall the previous year, Duchene sought draft advice from him over the course of the season.

[3] While playing in junior, Duchene drew comparisons to such NHLers as Steve Yzerman and Joe Sakic, as well as Mike Richards.

[6] Duchene recorded his first career NHL point in his Avalanche debut on 1 October 2009, against the San Jose Sharks with an assist on a powerplay goal by John-Michael Liles.

[12] On 6 April 2010, Duchene scored the game-winning shootout goal in a 4-3 win over the Vancouver Canucks to clinch the Avalanche a berth in the Stanley Cup playoffs.

[19] During the contest, he became the first player in All-Star Game history to be awarded a penalty shot when Washington Capitals forward Alexander Ovechkin tossed his stick toward Duchene on a breakaway.

[20] Soon thereafter, Duchene recorded his 100th career NHL point on 26 January with a goal against Phoenix Coyotes goaltender Ilya Bryzgalov in a 5–2 loss.

[26] The following day, on 9 December 2012, Duchene continued to remain in Europe to sign a one-month contract, with the option for the remainder of the lock-out, with HC Ambrì-Piotta of the Swiss National League A.

On 31 March 2014, the Avalanche announced that Duchene would likely miss four weeks with a knee injury after colliding with teammate Jamie McGinn during a game against the San Jose Sharks.

The trade saw the Avalanche acquire Sam Girard, Vladislav Kamenev and a second-round draft pick in the 2018 NHL entry draft from the Predators, as well as Andrew Hammond, Shane Bowers and first- and third-round picks in 2018 from the Senators; the Predators acquired Kyle Turris from the Senators.

On 29 October 2018, Duchene was one of multiple Senators players caught on tape in an Uber disparaging their then-assistant coach, Martin Raymond.

[35] On 22 February 2019, Duchene was traded (along with Julius Bergman) to the Columbus Blue Jackets for prospects Vitalii Abramov, Jonathan Davidsson, and conditional first-round draft picks in 2019 and 2020.

The Blue Jackets qualified for the 2019 playoffs as the Eastern Conference's final wildcard team, upsetting the top-seeded Tampa Bay Lightning in four games[38] before falling to the Boston Bruins in the next round.

[42] Following his buy out from the Predators, Duchene was promptly signed at the opening of free agency to a one-year, $3 million contract with the Dallas Stars for the 2023–24 season on 1 July 2023.

[43] Duchene played his 1,000th NHL game on December 7, 2023,[44] recording an assist on a Mason Marchment second-period goal as the Stars defeated the Washington Capitals 5–4 in a shootout.

[3] Following his rookie season in the NHL, Duchene was named to the senior Canadian team's roster for the 2010 IIHF World Championship in Germany.

[52] After signing an NHL lock-out contract in Switzerland with HC Ambrì-Piotta in 2012, Duchene was added to Canada's roster for the annual 2012 Spengler Cup.

In four games, Duchene scored five points and was selected as the centre to the All-Star Team in helping his nation win the Spengler Cup for the first time since 2007.

[54] At the 2015 World Championship, where Canada won the gold medal for the first time since 2007 with a perfect 10–0 record, Duchene finished in a tie for third in scoring with four goals and eight assists.

He was a die-hard Avalanche fan growing up and had jerseys for Joe Sakic and Patrick Roy, his former general manager and head coach, respectively, with Colorado.