Born in Bignona, Diarra began his senior career with Dakar UC, becoming the Senegal Premier League top scorer with nine goals in the 2002–03 season.

[3] He subsequently moved to Jeanne d'Arc, partnering Dame N'Doye on the team that reached the CAF Champions League semi-finals during the 2004 campaign.

[9] He made his competitive debut for the side in a UEFA Cup qualifier against his former club Zrinjski Mostar on 19 July, scoring a hat-trick in a 6–1 away victory.

[12] Throughout the league campaign, Diarra confirmed himself as one of the club's key players, along with two other foreign reinforcements, Juca and Almami Moreira, scoring 12 goals in 31 fixtures, as Partizan won the title after three years.

[13] On 6 August 2008, Diarra scored his first goal of the season in a 2–0 home win over Inter Baku in the second leg of the UEFA Champions League second qualifying round.

[15] Diarra continued his good form by equalizing the score versus Sampdoria in the UEFA Cup group stage, on 24 October, however Partizan would go on to lose the game 2–1.

On 27 October, in a league game against Al Wahda, Diarra suffered a fracture in his lower left leg,[21] spending the rest of the season in the process of recovering.

[22] After completing his loan spell, Diarra returned to Serbia and made his first appearance back for Partizan in a 5–0 home win over Novi Pazar on 13 August 2011.

[26] He played his last match for Partizan on 20 May, scoring the team's only goal in a 1–0 home win over Metalac Gornji Milanovac, celebrating his fourth league title.

He immediately established himself as the club's leading striker, scoring 13 league goals in his debut Süper Lig season, missing only one out of 34 matches.

On 14 October 2009, Diarra made his full international debut for Senegal after coming on as a 79th-minute substitute for Demba Ba in a 2–0 friendly loss to South Korea.