His older brother, Evan is also a footballer and they were teammates at UCD, St Patrick's Athletic and Sligo Rovers. In addition to playing football, McMillan is also a qualified architect.
Club career
Early years
Between 2000 and 2007, McMillan attended Wesley College, Dublin where he studied for his Leaving Cert.[1][2] As a schoolboy he played for Templeogue United and Mount Merrion Youths. He initially attended UCD games when Templeogue United supplied the club with ballboys. Mount Merrion Youths were effectively UCD's schoolboy team and his brother Evan also played for them.[3][4][5]
In 2011 McMillan began studying at UCD for his master's degree in architecture. After spells with St Patrick's Athletic and Olympic F.C., McMillan also re-joined UCD A.F.C. midway through the 2012 season. His eight goals in 15 league appearances helped UCD avoid relegation. In 2013, he also helped UCD win the Collingwood Cup for a third time, scoring the only goal in the final against UCC.[12][15][16]
In July 2013 McMillan signed for Sligo Rovers.[21] McMillan scored on his debut for Rovers, a 3–1 defeat to Cork City. This proved to be his only goal in 13 league appearances over the remainder of the 2013 season. He also played for Rovers in their 2013–14 UEFA Champions League games against Molde FK. However having played for UCD in the early rounds, McMillan was cup-tied and he missed out on Rovers successful 2013 FAI Cup campaign.[14][19][22]
While playing for Dundalk, McMillan has also been employed as an architect by O'Brien Finucane Architects, a company based in Dawson Street, Dublin.[1][6][23]
St Johnstone
McMillan signed a contract running to the summer of 2020 with Scottish Premiership club St Johnstone in December 2017.[33] He made his debut on 27 January 2018, as a substitute at home to Partick Thistle, however he only lasted 21 minutes before having to go off injured.[34] The hamstring injury he sustained kept him out for nearly three months.[35] On 5 May 2018, McMillan scored his first goal for St Johnstone, in a 5–1 win away at Motherwell.[36]
He moved on loan to Hamilton Academical in January 2019.[37] On 4 September 2019, McMillan joined Falkirk on a season-long loan.[38] McMillan left the Saints in July 2020.[39]
On 23 February 2023, McMillan publicly announced his retirement from professional football at the age of 34, stating "I would never have dreamed of coming through and doing the things I did" during his career.[46]