Metz In the summer of 2015, Diallo was promoted to the senior team at
Metz. He played 17 games in his debut season with the club, scoring 9 times. He appeared in 19 matches for Metz during the
2016–17 Ligue 1 season, scoring once. In January 2017, he was sent out on loan to
Brest for the remainder of the season after falling out of favour with new manager
Frédéric Hantz. Diallo had a successful time in Brittany, playing 16 times and scoring 7 goals. He went back on loan to Brest in the summer 2017 under the management of
Jean-Marc Furlan. He spent the entire season there as Brest finished 5th and he scored 9 goals in 33 games in
Ligue 2. After returning from his loan, Diallo had a prolific season with Metz, winning the
Ligue 2 title and scoring 26 league goals in 37 games in the process, only bettered by
Gaëtan Charbonnier who played for Diallo's old club Brest, scoring 27 times. Diallo was included in the year-end
UNFP Ligue 2 Team of the Season squad alongside 6 of his Metz teammates. Diallo immediately got up to life in
Ligue 1, scoring 6 times in his first 8 matches. In the January window he was subject to interest and a reported bid from
Premier League club
Chelsea, but no move materialised. By the time the Ligue 1 was suspended in March 2020 due to the
coronavirus pandemic, Diallo had contributed 12 goals with Metz sitting in 15th position in the table.
Strasbourg On 5 October 2020, Diallo signed a five-year contract with
Strasbourg for a fee of 10 million euros plus bonuses, making it the most expensive transfer in the club’s history. The move was poorly received by some Metz supporters, long-standing rivals of Strasbourg, who vandalized their club’s headquarters in retaliation. He made his debut on 18 October, replacing
Lionel Carole before halftime in a
Ligue 1 home match against
Olympique Lyonnais. Trailing 3–0, Strasbourg came back to 3–2, notably thanks to a goal from the Senegalese striker, who scored shortly after coming on.
Al-Shabab On 14 August 2023, Diallo joined
Saudi Pro League club
Al-Shabab for a club record €20 million.
Damac (loan) On 26 August 2024, Diallo joined
Saudi Pro League club
Damac on loan. Who chose against signing him permanently not wanting a fee installment.
Return to Metz On 31 August 2025, Diallo signed a three-year contract with
Metz, newly promoted to
Ligue 1. He missed the chance to score his first goal in his debut match against
Angers SCO on 14 September 2025, failing to convert a penalty. In the following match, this time against
AS Monaco, Diallo scored his first goal since returning to Metz with a low angled shot after receiving a pass from
Cheikh Sabaly. ==International career==