So who is the young centre-back worth £50 million?
We know of one who has been mentioned with a £40 million figure.
Sky Sports News reporter Kaveh Solhekol reveals Chelsea are very keen to sign a centre-back from a Premier League rival who is worth up to £50m.
He told The Transfer Show: "I think the targets they are looking at are wide players and also a striker.
"They are in for Wilfried Zaha but it will difficult to sign him from Crystal Palace, they do not want to sell him but it is significant that he has changed agents and will now be represented by Pini Zahavi. He's close to the Chelsea owner Roman Abramovich.
"There is also Jadon Sancho but he will cost a lot of money - he could could over £100m. That is a deal that is more likely to happen in the summer if he were to leave Germany.
"There is Moussa Dembele, we know they are interested in signing him from Lyon, but we are being told that he would like to come back to England but Lyon really want to hold on to him because of their injury problems.
"Then there is the left-back situation where their dream signing would be Ben Chilwell, but again it would be almost impossible to sign him from Leicester because they are not going to sell him.
"There is one other player whose name has been mentioned to me, he is a central defender at a rival Premier League club. We have been told Chelsea are very keen on signing him and some of the agents that are involved in the deal think it could happen this month. A young, very promising centre-back who would cost at least £50m."