Louhans-Cuiseaux, Diarra received his first red card of his career after incurring two yellow card infractions in a 2–1 defeat to Le Mans. Louhans-Cuiseaux finished the campaign in last place and were relegated to the semi-professional Championnat National, the third division of French football. After the season, Louhans-Cuiseaux attempted to tie down Diarra on a long-term deal and offered the player a trainee contract. Diarra refused the deal and was subsequently available to sign with any club on a free transfer. Bayern Munich During the summer of 2000, Diarra was signed by German club Bayern Munich after the club saw him play one match with Louhans-Cuiseaux. Upon his arrival to the club, he was immediately placed onto the club's reserve team, Bayern Munich II, in the Regionalliga Süd, the (then) third level of German football. Diarra was a regular within the team playing alongside the likes of Owen Hargreaves, Philipp Lahm, Bastian Schweinsteiger, and Zvjezdan Misimović. In his first season with the reserve team, he appeared in 28 matches scoring four goals. Diarra's influence in the team was immediate as he scored his first goal for the team in the first league match of the season against VfR Mannheim in a 4–2 defeat. His combative style of play also began to take shape as he collected nine yellow cards during the campaign with seven of them coming in the team's first 17 matches. The season was ultimately a success for Diarra partly due to the player being promoted to the senior team for the 2001–02 season by manager Ottmar Hitzfeld. He was assigned the number 30 shirt. Diarra began the 2001–02 season by making the bench in several of the team's league matches in August and September, but failing to make an appearance. In October 2001, he was dropped back down to the club's reserve team and appeared in four matches before earning promotion back to the senior team for its 2001 Intercontinental Cup showdown with Argentine club Boca Juniors. Diarra made the bench for the match, but did not feature as Bayern won the match courtesy of an extra time goal from Samuel Kuffour. The victory gave Diarra his first major honour of his career. Afterwards, he returned to the reserve team and later suffered an injury, which required a lengthy absence. Diarra rejoined the team in March 2002 under new manager Hermann Gerland and made nine more appearances.