The Edmonton Oil Kings of the Western Hockey League (WHL) selected Guenther with the first pick of the 2018 WHL bantam draft.[3] He debuted with the Oil Kings late in the 2018–19 season, scoring three goals and four points in his first eight WHL games. Guenther finished third on the Oil Kings in scoring in 2019–20, amassing 59 points (including a team-leading 26 goals) in 58 games.[1] As a result, Guenther was awarded the WHL's Jim Piggott Memorial Trophy as WHL rookie of the year.[2] During the pandemic-shortened 2020–21 season, Guenther scored 12 goals and 24 points in just 12 games. Guenther was awarded the Central Division's Player of the Year award and Most Sportsmanlike Player.[4]
The NHL Central Scouting Bureau ranked Guenther as the fifth-best North American skater eligible for the 2021 NHL entry draft.[1] On July 24, 2021, the Arizona Coyotes selected Guenther with the ninth overall pick in the 2021 draft; the pick was acquired in a trade with the Vancouver Canucks.[2] He was later signed to a three-year, entry-level contract with the Coyotes on August 31.[4]
In the 2021–22 WHL season, Guenther led the Oil Kings with 45 goals and 91 points. In the subsequent playoffs, Guenther again led the Oil Kings with 13 goals and 21 points, as they won the Ed Chynoweth Cup. He was also named to the WHL's Central Division First All-Star Team.[5]
Guenther began the 2022–23 NHL season with the Coyotes and made his NHL debut on October 15, 2022 in a 6–3 loss to the Boston Bruins.[5] He had a breakaway saved by Jeremy Swayman but registered an assist in his first game on a goal by Josh Brown.[5][6] Guenther scored his first NHL goal on October 22 against Anton Forsberg in a 6–2 loss to the Ottawa Senators.[7] Guenther played in 39 games with Arizona.[8] On January 10, 2023, the Seattle Thunderbirds acquired Guenther's WHL playing rights in exchange for seven draft picks. He was assigned to the Thunderbirds on February 5, 2023.[9] Guenther was assigned to the Thunderbirds at the 39-game mark due to a regulation that stated if a player played in 40 games, it would count as a year towards unrestricted free agency.[8] In the 2022–23 WHL season, Guenther played 20 regular season games with Seattle, recording 29 points. In the 2023 playoffs, Guenther led the Thunderbirds with 16 goals and 28 points, winning the Ed Chynoweth Cup for the second consecutive season. The Thunderbirds reached the final of the 2023 Memorial Cup, but were defeated by the Quebec Remparts.[10]
Guenther attended the Coyotes' 2023 training camp, but was assigned to Arizona's American Hockey League affiliate, the Tucson Roadrunners, to begin the 2023–24 season.[11] Guenther was recalled by Arizona on January 6, 2024 after Jason Zucker was suspended.[12] At the time, he was leading the Roadrunners in scoring with 10 goals and 18 assists in 29 games played.[13] Guenther made his season debut with the Coyotes on January 7, scoring one of the team's two goals in a 6–2 loss to the Winnipeg Jets.[14] He was judged to have performed sufficiently well that when Zucker was able to return to the roster, Guenther remained with the team.[15][13] With the Coyotes announced as relocating to Utah following the conclusion of the NHL season (though the franchise was treated as inactive, with the Utah Hockey Club being an expansion franchise), Guenther scored the team's penultimate goal in Arizona in its season-ending 5–2 victory over the Edmonton Oilers on April 17, before being transferred along with the rest of the Coyotes personnel to the new Utah franchise.[16]
In the 2024–25 season opener for Utah, on October 8, 2024, Guenther scored the first goal in franchise history against the Chicago Blackhawks. He later scored his second goal for the franchise on an empty net late in the third period of Utah's 5–2 inaugural win over Chicago.[17]
Guenther made his international debut for Canada as a member of the national under-18 team at the 2021 IIHF World U18 Championships.[18] Serving as an alternate captain, he registered three goals and four assists, helping Team Canada win the championship.[19]
