The 21-year-old has spent the season on loan at Werder Bremen in the Bundesliga playing 28 games, scoring six goals and creating another eight.
|5/4||Chelsea are 5/4 with Coral to lead at half-time and full-time against Rubin Kazan
"The conversation was very positive. They are pleased with his progress and think he is ready to become part of the first team," De Koster told the Evening Standard.
"The only problem is there is still no clarity about who is head coach next season."
The player himself admits that he may get shipped out on loan again next season if he is not a permanent fixture in the squad.
"Chelsea have told my agent that I must play for a big club if I don't stay at Chelsea in the summer and that I have to play at a higher level," De Bruyne told Kicker.