[citation needed] After a 2007 ruined by a recurring hamstring injury, Mackay made his debut for Adelaide in round 1 of the 2008 AFL season, in a loss to the Western Bulldogs.

[citation needed] He again was a regular for the side in 2009, playing 20 matches, and by this early stage of his career was rated a vital part of the Crows' young midfield.

[2] He returned late in the season and showed good form, impressing both with his offensive running and defensive pressure.

He recaptured his best form in 2014, playing 19 games, averaging 18 disposals and kicking a personal best 11 goals for the year.

[6] Mackay started 2015 in good form, laying a career-best 13 tackles along with 23 disposals against Melbourne in wet conditions in round 3.

[9] As part of his preparation for the 2017 season, Mackay spent as much time in the backline over the pre-season as he did in the midfield due to coach Don Pyke’s emphasis on flexibility.

[12] Mackay was dropped from several matches throughout the season and played for the reserves in the SANFL, where he was told to work on his toughness at the contest.

[13] When teammate Brodie Smith injured his anterior cruciate ligament, Mackay had to shift from his usual position on the wing to half-back to replace the former All-Australian in the finals.

This went against the precedent set earlier in the season where similar incidents, also resulting in head injuries, were not referred to the tribunal because the players involved were contesting the ball.