Middleton, 23, has appeared in 14 games this season for the Avs' American Hockey League affiliate, the Colorado Eagles, recording one point (0g/1a). He has totaled 27 points (10g/17a) in 116 career regular-season AHL contests with the Eagles and the San Jose Barracuda, where he spent the 2018-19 and 2019-20 campaigns. The 6-foot-5, 230-pound blueliner also appeared in four postseason contests for the Barracuda in 2019 and recorded a +2 rating.
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.
O'Brien, 26, has eight points (4g/4a) in 12 games this season with the Colorado Eagles, the Avs' AHL affiliate. He's tied for second in goals and fifth in points. The 6-foot-1, 213-pound center has skated in 17 career NHL games, all with the Washington Capitals, recording two points (1g/1a). He appeared in a career-high 13 contests with Washington during the 2014-15 campaign.
Signed by Washington as a free agent on Oct. 6, 2014, O'Brien spent six seasons in the Capitals' organization, O'Brien has collected 145 points (67g/78a) in 382 career AHL regular-season games with the Hershey Bears, Washington's AHL affiliate, and the Eagles. He has appeared in 44 career playoff games with Hershey, totaling 13 points (8g/5a). In 2016, he tallied six points (4g/2a) in 20 postseason outings to help the Bears advance to the Calder Cup Final, where they fell in four games to the Lake Erie Monsters.
Prior to turning pro, O'Brien played four seasons in the Quebec Major Junior Hockey League, where he produced 95 points (42g/53a) in 261 career contests with Rimouski Oceanic and the Rouyn-Noranda Huskies. He added eight points (4g/4a) in 30 QMJHL playoff games and served as an alternate captain for Rouyn-Noranda in 2012-13 and team captain for the 2013-14 campaign.
