Diatta moved to France when he was only one year old. He was the holding force in the centre of Senegal's defence, and is also tough in the air, which provides a threat in attacking set-pieces.
Before moving to Olympique Lyon in 2004, Diatta played 142 games for Stade Rennais, scoring 9 goals in that time. Before his time at Rennes, he was at Marseille, but never actually played a game for them. Diatta's first club was Toulouse FC. He spent one season there and played 25 games without scoring. In his first year (2004/2005) with Lyon he played 19 games. During his second year (2005/2006) at Lyon, he was troubled with injury and only makes 13 appearances also without goals. On August 2006, he left Lyon on free transfer in search for regular team football, settling at St. Étienne.
On 7 March 2008, after a week's trial at Newcastle United, Diatta agreed a short term deal until the end of the season after buying out his contract at Beşiktaş J.K.. The deal was finally confirmed by the club on 14 March after a week of confusion. He made his first team debut for Newcastle as a substitute in a Premier League match against Reading on 5 April but was released on 15 May.