Callum Hudson-Odoi has been told he will not be sold by Chelsea before Thursday's transfer deadline - or in the summer.
The 18-year-old is out of contract in June 2020 and has been linked with a £35million move to Bayern Munich.
Chelsea on Monday reportedly turned down a transfer request from Hudson-Odoi, with head coach Maurizio Sarri reiterating to the club's stance on Tuesday.
Speaking ahead of Wednesday's Premier League clash at Bournemouth, Sarri said: "On the pitch he's doing very well. I'm really very happy with him. I'm not very happy with the situation, but I know very well that every big team here in England has the same problem.
"It's not easy to keep these young players. He is of course one of the best 18-year-old players in Europe, so it's very, very difficult. The club told me he's out of the market for sure and probably he will be out of the market in July."
For Hudson-Odoi to stay into the 2019-20 season it would seem Chelsea must persuade him to sign a new contract.
Sarri insisted that is not his remit and the 60-year-old Italian would make no guarantees to Hudson-Odoi on match time.
The Italian added: "I cannot do anything, as you know very well. If I have the power to sign a new contract, I can do everything.
"It's impossible to promise him that he will play every match, because it depends on the situation."