Mouzakitis has been linked to several top European clubs.
Kovacevic revealed that Olympiacos rejected a €40 million bid from Brighton for the player over the summer.
He stated that the decision to reject the offer shows the club's confidence in Mouzakitis' potential and their belief that he can continue to develop.
Kovacevic praised Mouzakitis' maturity, saying that he has the level of maturity of a player in their thirties, despite being only 18 years old.
The sports chief also highlighted Mouzakitis' exceptional ball handling skills, describing him as a "gem" with a rare talent for his age.
