Sibiya is due to join Lille on loan with a view to making the move permanent, and Cardoso believes it is the right step for a player he feels has the talent to succeed.
"It is a fantastic opportunity,” Cardoso told reporters on Monday. “I coached in France, so I know very well the club he is going to, the facilities they have and the process they use to develop young players.
"At the same time, it is a very competitive environment he is going to face, but I think he is ready for the challenge. What will speak for him is not the level of readiness he has now, but the level of readiness he will develop there.
"There are still steps he needs to take before we see him in the first team in the future.”
Cardoso had a spell as coach of Nantes in 2018 and says French football is fast-paced and attacking.
"French football is very special,” he said. “You have to cope with players, especially up front, who are very athletic. It is a game with a lot of transitions and exploitation of space.
"Lille is a school of good football. As much as we know the player could have been a good player for the future of Sundowns, we also know he will be a good player for the future of South Africa."
Sibiya, who won the 2025 Under-20 Africa Cup of Nations with South Africa, made his Sundowns debut in a 2-0 win over Orbit College in January. He also featured in the Nedbank Cup and two CAF Champions League games.
He was on the bench for the second leg of the Champions League final as Sundowns lifted the trophy in Morocco against AS FAR.
With experienced Aubrey Modiba, Divine Lunga and Fawaaz Basadien in the first team, the 20-year-old has found opportunities limited.