Youth Diop moved to Spain at age 14 in 2011 to join Club Internacional de la Amistad, an academy for foreign players in
Palencia. After a spell at
Montañeros CF in
A Coruña, he joined
Celta de Vigo's youth setup in 2013.
Celta Diop made his senior debut with
the reserves on 23 August 2014, coming on as a second-half
substitute in a 2–0
Segunda División B away win against
CD Lealtad. He scored his first goal eight days later, netting the last in a 5–0 home routing of
UP Langreo. On 11 August 2015, Diop signed a new five-year deal with the club, running until 2020. He made his first team – and
La Liga – debut on 12 December of that year, replacing
Nolito in the dying minutes of a 1–0 home success over
RCD Espanyol. Diop scored his first goal in the main category on 27 November 2016, netting the last in a 3–1 home win against
Granada CF. The following 31 January, he extended his contract until 2021 and was definitely promoted to the main squad, being assigned the number 4 jersey.
Lyon On 29 August 2017,
Lyon announced the signing of Diop on a five-year deal. The transfer fee paid to Celta was reported as €10 million with €4 million of possible bonuses. On 14 August 2019, after featuring sparingly, he returned to his former side Celta on loan for the
2019–20 campaign.
Loan to Dijon On 6 August 2020, Diop signed for
Ligue 1 club
Dijon on loan for one season. The deal included an option to buy of €5 million plus an additional €1.5 million in bonuses, and a 15% sell-on fee clause. Diop made his debut for Dijon in a 1–0 loss to
Angers on 22 August 2020.
Later career On 29 June 2022, Diop signed a two-year contract with
Super League Greece club
Aris.
Free agent Diop joined
La Liga side
Elche on 14 February 2023 after a trial. He was signed to a contract on until the end of the season. On 6 March 2024, Diop joined
Slovak First Football League club
DAC Dunajská Streda on a contract until the end of the season with an option to extend. On 31 March 2026, Diop joined
Regional Preferente club
Promesas EDF. ==International career==