Championnat du Sénégal de football
Diop was born in Rufisque, Dakar. He began his football career with junior team Ndeffann Saltigue before joining ASC Diaraf of the Senegal Premier League in 1996. He left Senegal for Switzerland, where he spent a few months with third-tier club Vevey before signing as a professional for Ligue Nationale A club Neuchâtel Xamax in the 2000 close season. In December that same year, he joined fellow top-flight club Grasshoppers, whom he helped win the championship title in his first half-season and made his first appearance in UEFA competitions the next. He moved to France in January 2002 to join Lens of Ligue 1 on a five-and-a-half-year contract.