Middleton, 25, has recorded 20 points (3g/17a) in 51 games for the Avs' American Hockey League affiliate, the Colorado Eagles, this season. He ranks first among Eagles defensemen in assists and third in goals. The 6-foot-5, 230-pound defenseman has collected 63 points (15g/48a) in 224 career AHL contests with the Eagles and the San Jose Barracuda, where he spent the 2018-19 and 2019-20 campaigns. Middleton has added eight points (3g/5a) in 15 total AHL postseason contests.
During the 2020-21 season, Middleton made his first NHL appearance and skated in three outings with the Colorado Avalanche. He made his NHL debut on April 9, 2021 at Anaheim.
Selected by the Toronto Maple Leafs in the fourth round (101st overall) of the 2016 NHL Draft, Middleton played four seasons for the Ontario Hockey League's Saginaw Spirit, collecting 58 points (11g/47a) in 255 career outings while serving as team captain in his final two seasons. The Stratford, Ontario, native added two points (0g/2a) in 12 career playoff games with Saginaw.
Middleton suited up for Team Canada White at the 2014 World Under-17 Hockey Challenge, notching one point (0g/1a) in five games.