Born in Créteil, Saco joined Le Havre's youth sector in 2017, aged 15, before moving to Sochaux one year later. He then came through the youth ranks of the Lionceaux, taking part in the 2019–20 Coupe Gambardella, where Sochaux reached the round of 16 before the competition was cancelled, due to the emergency caused by the COVID-19 pandemic.
In October 2020, Saco entered AC Milan's academy; however, he was released after just one season, having not managed to break into the under-19 team consistently.
Napoli
In September 2021, he officially joined fellow Italian club Napoli after a successful trial.
Having impressed with his performances for Napoli's under-19 squad, during the 2021–22 season Saco started training with the first team, under manager Luciano Spalletti. The midfielder originally received his first official call-up to the senior team for a Serie A match against Juventus on 6 January 2022: however, having tested positive for COVID-19, he eventually had to withdraw from the match-day squad.
Loan to Pro Vercelli
On 15 July 2022, Saco joined Serie C side Pro Vercelli on a season-long loan. He then made his professional debut for the club on 3 September, starting and playing 90 minutes in a 1–0 league win against Padova. On 5 November, he scored his first professional goal in a 3–1 league loss against AlbinoLeffe.
Loan to Ancona
On 1 September 2023, Saco joined fellow Serie C club Ancona on loan for the remainder of the season.
Loan to Bari
On 30 August 2024, Saco moved on loan to Bari in Serie B.
Loan to Casertana
On 26 January 2026, Saco joined Casertana in Serie C on loan.
In July 2024, he was included by head coach Aliou Badra Diallo in the Malian squad for the men's football tournament at the Summer Olympics in Paris, where The Eagles were eventually eliminated in the group stage.
Style of play
Saco is a left-footed midfielder, who has been mainly regarded for his physical attributes, which allow him to win many headers and keep possession. Despite his slow pace, he has proved to have good abilities in reading the game and finding goal opportunities, thanks to his off-the-ball movement and his heading. He has also been noticed for his vision and his long-range passing prowess.
↑Regis, Sebastiano (15 July 2022). "BENVENUTO COLI SACO!". F.C. Pro Vercelli 1892 (in Italian). Archived from the original on 3 February 2023. Retrieved 3 February 2023.