The Brazil international turns 18 in April and will leave Palmeiras for Chelsea after the Club World Cup.
The Blues agreed a fee rising to €61m for Estevao in June and he has since won his first caps with Brazil.
Given his form for club and country, Chelsea management have already agreed to immediately add Estevao to the senior squad rather than loan him to French partners Strasbourg.
Blues manager Enzo Maresca said last week: "Yes, we are following him.
"He is doing fantastic but unfortunately he is doing fantastic there and not with us. We are going to wait until next summer when he will arrive here but for sure we are very happy in the way he is doing these things.
"No, no, no (I haven't spoken to him). I have so many players to speak to (laughs). No, I didn't speak with him."