Wagner was born on June 23, 1997, in Calgary to parents Kevin and Linda and older brother Tyler.
Playing career
Although Wagner began playing hockey at the age of three, he also played lacrosse before fully committing to hockey. Wagner began his hockey career with the Blackfoot Minor Hockey Association before joining the Calgary Northstars. Although he played for the Calgary Northstars on the Bantam AA Blazers during their 2010–11 season, his playmaking ability and skill earned him a promotion to Midget AAA. During his AAA years, Wagner played for Team Calgary North at the 2012 Alberta Cup and Team Alberta at the 2012 Western Canada U16 Challenge Cup.
Major junior
Wagner was drafted in the 5th round of the 2012 WHL Bantam Draft by the Regina Pats at the age of 16. After attending the Pats training camp, he signed agreed to a contract with the team. He scored his first WHL goal in the first period of a 4–3 shootout loss to the Medicine Hat Tigers on December 15, 2013. After his rookie season, in which Wagner scored 2 points in 42 games, the Pats changed coaches to John Paddock which Wagner says contributed to his production increase in his sophomore season. His sophomore year proved to be his breakout season with the Pats, as he scored 39 points in 61 games and was drafted 99th overall by the Los Angeles Kings in the 2015 NHL Entry Draft. Leading up to the draft, Wagner's final ranking by the NHL Central Scouting Bureau was 35th overall amongst North American skaters and third in Anaerobic Fitness: Peak Power Output. He attended the Kings training camp prior to the 2015 season but was returned to the Pats on September 24, 2015. Upon his return, Wagner once again had a breakout season and set new career highs with 62 points in 70 games. Wagner again attended the Kings training camp prior to the 2016 season but was returned to the Pats on October 1, 2016. The 2016–17 season was another breakout season for Wagner, as he set new career highs in goals and assists. That season, the Pats qualified for the WHL playoffs. Wagner scored a goal in Game 6 of the Eastern Conference Championships against the Lethbridge Hurricanes to help push the Pats to the WHL Championship round for the first time since 1984. He ended the playoffs with 21 points in 22 games as the Pats ended up losing the WHL Championship Finals series to the Seattle Thunderbirds 4–2. As a result of his breakout season, Wagner was selected to attend the Canadian National Junior Team camp prior to the 2017 World Junior Ice Hockey Championships but he failed to make the final roster.
Professional
On March 6, 2017, Wagner signed an entry level contract with the Los Angeles Kings. During the off-season prior to the 2017–18 season, Wagner required shoulder surgery to repair a torn labrum and dislocated bicep tendon. After he was medically cleared to play, Wagner was assigned to the Kings American Hockey League affiliate, the Ontario Reign. Upon joining the AHL for his first season, he scored his first professional goal on December 9, 2017, in a 4–2 loss to the Texas Stars. Wagner attended the Kings 2018 training camp, where he earned praise from teammates and coaches including Coach John Stevens who said, "He’s an explosive athlete, so he’s got extreme quickness and speed." Having made the Los Angeles Kings opening night roster for the 2018–19 season, Wagner made his NHL debut on October 5, 2018, in a 3–2 overtime loss to the San Jose Sharks. After playing in seven games for the Kings, Wagner and teammate Sean Walker were reassigned to Ontario Reign. During the first two months of the season, Wagner played 11 games with the Kings and five with the Reign. Following a rash of injuries, Wagner scored his first career NHL goal on November 21, 2018, in a 7–3 loss to the Colorado Avalanche. Although he missed four games due to a lower body injury, Wagner recorded 10 goals and seven assists within his first 50 games. Prior to the trade deadline, he played alongside Nate Thompson, who he considered a mentor, before joining Trevor Lewis and Kyle Clifford as their winger. At the end of the season, he was awarded the team's Jim Fox Community Service Award.
