[1] Mackay was a key contributor for his junior team, the Spruce Grove Saints, and helped them capture back-to-back AJHL championships.
As a reward for his leadership and defensive play, Mackay was named as an alternate captain for his junior season and responded by increasing his point total once more.
[3] Mackay only recorded one more assist in the tournament but his steady defensive play helped the Bulldogs win three consecutive 2–1 decisions en route to a national championship.
Mackay again led the way, scoring the opening goal less than 4 minutes into the contest and added an assist on the insurance marker.
Due in part to the COVID-19 pandemic, Mackay travelled to Europe for his second season of professional hockey and had a bit of a resurgence with the Graz99ers.