Doku, who turned 18 today, has been consistently linked with a move to English powerhouse Liverpool.
The youngster visited Liverpool's facility in 2018 but opted to stay with the Belgian giants.
And his former coach Hein Vanhaezebrouck, who is a huge admirer of the Belgian-born Ghanaian believes the forward has the quality to be better than iconic Eden Hazard.
"His left foot is currently just mostly to lean on. There is still a lot of work to do”, Vanhaezebrouck told Belgian daily Het Nieuwsblad.
"Defenders now know that they should not cover his left, that they can let him kick a cross with it.
“If he perfects his left [foot], he is fully capable of reaching the top.
"Then he will even surpass Hazard in terms of potential.
“But that's [something that needs] training, training, training.
"Hazard is eleven years older, give him time.”
Doku has a contract with the Purple and Whites until the summer of 2022.