Chelsea have no intention of selling Callum Hudson-Odoi now, 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 before Thursday's transfer deadline.
Chelsea reportedly turned down a transfer request from Hudson-Odoi on Monday, with head coach Maurizio Sarri reiterating the club's stance on Tuesday.
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 game time.
Sarri said: "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."
Hudson-Odoi scored his second Chelsea goal on his sixth start of the season in Sunday's FA Cup fourth-round win over Sheffield Wednesday.
He has made five additional substitute appearances, three of those in the Premier League.
His first Premier League appearance came on Boxing Day at Watford, with Bayern's interest already known, and he is yet to start in the top flight.
Speaking ahead of Wednesday's Premier League clash at Bournemouth, when Hudson-Odoi is likely to be on the substitutes' bench again, Sarri added: "He's improving. I think he'll be the future of our club. He will be the future of English football."
Sarri had hoped to make two signings this month. Only Gonzalo Higuain has arrived so far, on loan from Juventus, and the head coach is keen to recruit a replacement for Cesc Fabregas, who has left for Monaco.
Sarri added: "I thought for us it was important to have two players. One has arrived. I am waiting for the other.
"If he will arrive, I will be very happy, otherwise I have to work with these players. It's not a big problem for me."
Ethan Ampadu was deployed in the central midfield position where Jorginho is first choice, but the 18-year-old Wales international fared poorly, Sarri said.
Higuain made his debut against Wednesday, afterwards telling Sarri "they are so aggressive".
Sarri told him it was "normal" and expects the striker, who scored 36 Serie A goals in 35 appearances for Sarri's Napoli in 2015/16 to quickly adapt to the rigours of English football.
Higuain is likely to make his Premier League debut at Bournemouth, alongside Eden Hazard, who thrived returning to his favoured left-wing position in last week's Carabao Cup win over Tottenham.
Higuain turned down Willian's offer to take a penalty in the win over Wednesday, which surprised Sarri, who says it showed the 31-year-old Argentina international's team ethic.
Sarri said: "He wants to score in every match. I think it was a wonderful start, because it means he's available to the team-mates."
The Italian could offer no clarification on the futures of midfielder Danny Drinkwater or defender Gary Cahill, who are both out of favour.