Career
An Aspire Academy youth graduate, Diallo joined K.A.S. Eupen in July 2014. On 30 January 2015, having featured regularly during the first part of the season, Diallo signed with Valencia CF and was assigned to its reserve team, in Segunda División B. He made his first-team debut on 2 December, starting in a 3–1 success at Barakaldo CF for the Copa del Rey.