Similar to his stint at Bastia, Diarra was included in the team as a starter by coach Joël Muller. The season was a major success for Diarra as he was the only player in the team to start every league match he played for the club. He also served as captain for a majority of the season. His consistent performances led to his call up to the senior national team. Diarra scored his first goal of the campaign in a 1–1 draw with Ajaccio. He scored the goal in the opening minute of the match. On 6 February 2005, Diarra scored the opener in team's 2–0 win over Paris Saint-Germain at the Parc des Princes. He finished the campaign with 37 total appearances and two goals. Diarra also collected 11 yellow cards.
