Although spending the vast majority of his first campaign appearing with the youth squad, Diakité made his first-team – and Serie A – debut on 1 April 2007, replacing Guglielmo Stendardo in the dying minutes of a 4–2 away win against Udinese. His first start came late in the month, in a 0–1 home loss against Fiorentina, also having a goal disallowed.