In 2013, he moved to Leonardtown, Maryland, where his father was stationed as a member of the Royal Air Force, and Gillan began playing American football in high school there.

[1] He then went on to play college football at Arkansas–Pine Bluff,[2] receiving the scholarship offer through a Facebook invitation.

[15][16] He kicked several field goals in a preseason game against the Bengals following an injury to Graham Gano,[17] and made the 53 man roster.

[18] On 12 December 2022, while playing in a game against the Philadelphia Eagles, Gillan was flagged for a rare illegal kick penalty.

While attempting a punt, Gillan fumbled the snap and kicked the ball after it bounced off the ground.

[20] On 17 December, Gillian successfully kicked a 40–yard field goal against the New Orleans Saints, in relief for injured kicker Randy Bullock.