In late August 2014, he joined Stade Rennes from SC Freiburg for a reported transfer fee of €1.5 million signing a three-year contract.[1][2]
In early July 2016, Diagne signed for Werder Bremen. The transfer fee was estimated at €1.5 to 2 million.[3][4] On 10 January 2017, Diagne joined Ligue 1 club Metz on loan, rejoining his former club until the end of the 2017–18 season.[5][6]
In August 2018, Diagne joined Süper Lig side Konyaspor signing a two-year contract with the option of a third year.[7]