Koulibaly, who is now in the Saudi Pro League, praised Chelsea forward Nicolas Jackson.
The Al Hilal defender sees his Senegal teammate as someone who can win the Ballon d’Or in the future.
He told talkSPORT's Saudi correspondent Ben Jacobs: "For me, Nicolas can be a very good player. He's still young, everybody was wanting more from him last year but you can't forget that he's a young player.
"Me and Edouard Mendy speak a lot with him because we know it's difficult when you arrive at a big club like Chelsea.
"It's true that in Chelsea, the demand is really high. They want a lot of goals, a lot of assists, they want you to be a very good player from the beginning.
"But we know Nicolas can be very good, I know him. We give him advice because he deserves it and he's a player who listens."