Diagne was described as a big talent in his younger years, and he also played a reserve team match for Copenhagen at the age of 15 in October 2021.
In the fall of 2023 Diagne trained with AaB and in January 2024 the club's sporting director Ole Jan Kappmeier confirmed that they had signed him.
[3] Already in the spring, Diagne was twice part of AaB's match squad in the Danish 1st Division and on April 17, 2024, after just four matches in the club's U-19 squad, the club confirmed that they had extended with Diagne until June 2028.
[4] On June 2, 2024, Diagne made his official debut for AaB when he replaced Younes Bakiz in the 80th minute and managed to make an assist for Melker Widell's 4–1 score.
[7] On August 18, 2024, Diagne made his debut in the Danish Superliga in a match against Brøndby IF.