Regan is a centre back who joined Manchester United in September 2015 from Newport County. He had previously been at Cardiff City and in 2014 had trials with Manchester United. As a 16 year old he made his debut for Newport County during the 2014/15 season in League 2.
Despite joining Manchester United in September 2015 he had to wait until January 2016 for international clearance and was included in his first competitive game in February 2016 for the Under-21 side. He was an unused substitute for the First Team in February 2016 away at FC Midtjylland and made his debut as a late substitute in the return leg at Old Trafford. Although eligible for the Under-18 side in his first season, he never made an appearance for them.
Regan continued as a regular in the Under-23 side in the 2016/17 season. He was sent off for a two footed tackle at home to Manchester City in January 2017. He was sent off again for the Under-23 side away to Sunderland in March 2017.
Regan joined Northampton Town on loan for the 2017/18 season.
In January 2019 Regan joined Newport County on loan.
He was released by Manchester United at the end of the 2018/19 season and signed for Milton Keynes Dons.