SABC Sport reported last week that the U20 international was being earmarked for a move to Europe, with Lille now confirmed as his destination. The French club has built a reputation for developing emerging talent.
Sibiya will initially join on loan, with Cardoso encouraging the youngster to make the most of the opportunity and work towards making the move permanent.
"Regarding Thato, fantastic opportunity. As you know, I coached in France, so I know the club very well where he is going. I know the facilities they have and the stability they maintain in terms of the development processes for young players and the final stage of formation for young players. At the same time, it's a very competitive environment he will face. Obviously, I think he's ready for the challenge," said Cardoso
"What will speak for him is not the level of readiness he has, but the level of readiness he will still develop there."
The Portuguese mentor added that Sibiya, who featured in the U20 FIFA World Cup for South Africa last year, will not feel out of place in France.
Sibiya was promoted to the senior team in January last year and Cardoso admitted it wasn’t easy for Sundowns to let go, but it was important.
"As much as we believe the boy could be an important player for Sundowns in the future, we also believe he will be an important part of South Africa's future. It's an opportunity that is obviously difficult to say no to, and the club had to eventually protect their own rights in this situation. So we are excited about that; we want to see him succeed, and we want to see him show the character he needs so that he also speaks about what kind of players we develop at the club."
The coach also took the chance to slam suggestions that Sundowns are often reluctant to sell their players abroad.