Crusaders 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. His performances led to him being selected to represent an Intermediate League XI. The club had previously sold
Jimmy Nelson to
Cardiff City in 1921 where the Scotsman had impressed. Cardiff subsequently approached Crusaders to enquire "Have you any more players like Jimmy?" This correspondence ultimately led to Sloan and
Tom Watson joining Cardiff. 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, while Scottish side
Third Lanark had also expressed interest in his signing. Alongside his playing career with Crusaders, Sloan had served as a policeman until his departure from the club in 1924.
Cardiff City Sloan completed his
transfer to Cardiff in May 1924, alongside fellow Irishman
Paddy McIlvenny, 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. He was forced to wait until the second half of the
1924–25 season before making his senior debut for the club. With Keenor absent on international duty, Sloan started in a 1–1 draw with
Notts County on 14 February 1925 in a side without six first team regulars due to international call-ups. He appeared only four further times during the remainder of the campaign, covering for Keenor on each occasion. making 31 appearances in all competitions as Cardiff finished 16th in the
First Division. The following year, Sloan again began the season as backup; he made his first appearance of the campaign in a 2–0 defeat to
Manchester United on 25 September. His start to the year was also disrupted by a back injury. In late December 1926, Sloan regained his first team place and appeared in 18 of the remaining 24 games of the league season. His return to the side also led to him playing all 7 matches of the club's
FA Cup run, 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". Two weeks after their FA Cup victory, Sloan helped Cardiff complete a cup double by winning the
Welsh Cup final, defeating
Rhyl 2–0. He made 27 league appearances over the following two years which culminated in Cardiff's relegation to the
Second Division at the end of the
1928–29 season. His only goal for Cardiff came in a 1–1 draw with Arsenal during his final year with the club. The pair eventually left the club return to Ireland and join
Linfield in June 1929. He was appointed club captain on his arrival although his early months were hampered by injury. In his first season, Sloan was selected to captain an Irish League XI against their counterparts from the Irish Free State. He helped the side to a double by winning both the
Irish League and
Irish Cup. In the cup final against
Ballymena, the
Ballymena Observer noted that Sloan and his two half back teammates had "carried them (Linfield) to victory" as his side won 3–0 to retain the trophy. As team captain, Sloan was presented with the trophy by the president of the
Irish Football Association. Along with Watson, the victory completed an unusual Treble for Sloan, having won the major cup competition in three countries after already having won the FA Cup and the Welsh Cup. He helped Linfield repeat their double success the following year and remained with the side until 1932 when he was released. During his playing career, he acquired the nickname "sticky" Sloan which remained with him throughout the remainder of his time in football. ==International career==