He was primarily a forward, modeling his style of play after Mikko Koivu, but switched positions when Minnetonka High School needed another defenseman.

After his time in the development program, Miller spent two seasons with the Wisconsin Badgers while also appearing in two consecutive IIHF World Junior Championships.

As a rookie playing alongside Jacob Trouba, Miller established himself as a part of the Rangers' young core, consistently seeing over 20 minutes of ice time per game and earning NHL All-Rookie Team honors at the end of the season.

[2] Originally a forward on his youth hockey teams, Miller's role model was Mikko Koivu, longtime captain for the Minnesota Wild.

[4] After registering five goals and 11 assists during his second season with Minnetonka, Miller left his high school to join the USA Hockey National Team Development Program (NTDP).

[9] Newly appointed Wisconsin head coach Tony Granato had voiced a desire to build the Badgers' 2018–19 season around their young defensemen, and Miller was partnered with fellow freshman Ty Emberson.

[11] By Wisconsin's holiday break, Miller led the team with 17 points and had been twice named the Hockey Commissioners' Association National Rookie of the Month, for October and December.

[14] Following his successful freshman campaign, Miller entered the 2019–20 NCAA season as one of only two unanimous selections to the preseason All-Big Ten First Team.

[17] These pandemic disruptions left it unclear if Miller, who was already joining an unusually young defensive corps, would begin the 2020–21 season with the Rangers, or if he would need an extra year of development in Hartford.

[24] Although the Rangers struggled in the NHL's difficult East Division and missed the 2021 Stanley Cup playoffs,[a] Miller, Alexis Lafrenière, and Kaapo Kakko anchored a core of players aged 22 or younger who sportswriters saw as capable of leading the team through future seasons.

He became the 4th defenseman in Rangers franchise history for the "latest game-tying goals", joining Brian Leetch (1998), Darren Turcotte (1992), and Doug Robinson (1965).

[30] A hearing was subsequently held with the NHL's player safety department and Miller was issued a three-game suspension for unsportsmanlike conduct.

[35] In a statement released on Twitter after the Q&A, Miller said that he had been the subject of similar racialized incidents throughout his hockey career and that he chose not to quit the sport out of love for it.