Amateur
After playing two years of hockey at Barrington High School near his hometown of Tower Lakes, Illinois between 2012 and 2014, serving as team captain in his final year, Mackey spent the 2014–15 hockey season as a member of the triple-A level U18 Team Illinois in the High-Performance Hockey League (HPHL). [2]
Mackey began playing for the Green Bay Gamblers of the United States Hockey League (USHL) in 2015–16. He was named an alternate captain in 2016–17 and emerged as an offensive engine on a Gamblers squad that also featured future NHL first-round pick Casey Mittelstadt. Mackey led the team with 47 points in 60 games [3] and was named USHL Defenseman of the Year and to the USHL First All-Star Team. [4] He was recruited to join the Minnesota State Mavericks men's ice hockey team to begin the 2017–18 season. [5]
Prior to the start of his college career, Mackey was invited to and attended the Calgary Flames' 2017 summer prospect development camp as an undrafted free agent. [6] Beginning that fall, Mackey enjoyed a successful debut season with the Mavericks which saw him earn a spot on the 2017–18 Western Collegiate Hockey Association (WCHA) All-Rookie Team. In the summer of 2018, Mackey again attended an NHL prospect convention: this time, he was invited to the Buffalo Sabres' annual development camp. [7] He followed it up with a 2018–19 season during which he was named a WCHA All-Academic and to the All-WCHA Third All-Star Team. [4]
In 2019–20, Mackey, unaffiliated with any professional club after going undrafted, emerged as a top prospect and attracted interest from 28 of the NHL's 31 teams. He led Mavericks defensemen with 24 points in 36 games en route to being named to the All-WCHA First All-Star Team and the American Hockey Coaches Association's All-America West Second Team. [4] Mackey's performance in 2019–20 led TSN's Frank Seravalli to name him the top-ranked college free-agent on the market. [8]
Professional
On March 20, 2020, Mackey signed a one-year, entry-level contract with the Calgary Flames to take effect at the start of the 2020–21 NHL season. [9] Despite his contract not taking effect until the following season, Mackey joined the Flames for practices in the Edmonton bubble as part of the return-to-play program in the 2020 Stanley Cup playoffs. [10] Mackey made his NHL debut on February 13, 2021. [11]
During the 2022–23 season, Mackey remained on the Flames roster, primarily serving as a depth defenseman and healthy scratch. After 10 appearances with the Flames, Mackey was dealt at the NHL trade deadline along with Brett Ritchie to the Arizona Coyotes in exchange for Nick Ritchie and Troy Stecher on March 3, 2023. [12]
Following his brief tenure with the Coyotes, Mackey was signed as a free agent in the off-season to a one-year, two-way contract by the New York Rangers on July 1, 2023. [13] On March 1, 2024, he signed a two-year contract extension with the Rangers. [14]
United States 
