In 1978, he was part of the Ballymena United team that reached the final of the Irish Cup only to lose to Linfield.
Sloan's influence in the heart of the United midfield was not sufficient for him to earn a regular place in the team, but his four appearances in his first season at Old Trafford were enough to attract a call from the Northern Irish senior team at the end of the season.
In the space of 15 days, Sloan won his only three caps; two came in the 1979 British Home Championship, against Scotland and Wales, while the other was a UEFA Euro 1980 qualifying match against Denmark.
Sloan's involvement with the Manchester United first team gradually decreased over the next three seasons – he made just eight appearances in total in 1979–80 and 1980–81, and none at all in 1981–82 – and he was released to Chester in July 1982.
At Chester, Sloan found his niche, making nearly 50 appearances in the one season he spent there before he returned to Northern Ireland to play for Linfield.