He joined Football League First Division side Cardiff City in 1924 where he spent five years and made more than 90 appearances in all competitions.
In 1932, he was appointed player-manager of Portadown and led the club to their first senior trophy since joining the Intermediate League by winning the Gold Cup in 1934.
In 1939, Sloan stepped down as Portadown manager to enlist in the Royal Army Service Corps during World War II.
Sloan joined the British Army at the age of 18 before beginning his playing career in Ireland at the end of his service with Irish Intermediate League side Crusaders.
[5] Club manager Fred Stewart had been informed of Sloan in early 1924 and had travelled to Ireland in order to watch him play, only to find him suspended for the match in question,[6] while Scottish side Third Lanark had also expressed interest in his signing.
[9] On his arrival at the club, Sloan found his path to the first team blocked by the half back trio of Fred Keenor, Harry Wake and Billy Hardy.
[10] He remained a reserve for the opening matches of the 1925–26 season before making his first appearance of the campaign in a 6–3 defeat to Blackburn Rovers on 26 September 1925 in place of Hardy.
He retained his place for the majority of the season, largely over club captain Keenor,[12] making 31 appearances in all competitions as Cardiff finished 16th in the First Division.
His return to the side also led to him playing all 7 matches of the club's FA Cup run,[14] including the final where they defeated Arsenal 1–0 to become the only team from outside England to win the competition.
[16] In their coverage of the final, the Western Mail described Sloan as "impetuous at times, but on his day a dominating personality and a good shot".
[29] Sloan was selected to represent Ireland in a junior international fixture in March 1924, helping his side to a 2–1 victory over their Scottish counterparts.
[36] The club was struggling both financially and in results on his arrival, but Sloan guided the side to their first senior trophy since joining the Intermediate League by defeating Glentoran in the final of the 1933–34 Gold Cup.
[34] Ahead of the 1935–36 season, Sloan was presented with a new bedroom suite having helped stabilise the club's finances with the sale of three players, including Ben Clarke.
[44] Following the outbreak of World War II, Sloan stepped down from his position with Portadown and enlisted in the Royal Army Service Corps as a private.
[45] Within a year, he was promoted to corporal and then sergeant,[46][47] while his previous footballing experience led to him refereeing amateur matches while stationed in France.
[50] He rejoined Portadown in 1942 to assist in the running of the newly formed reserve side at the club alongside Norman Corner,[51] before joining Cliftonville as a scout the following year.