Chelsea have been alerted to Matthijs de Ligt's contract stand-off with Juventus.
The Holland defender is reluctant to agree new terms with his current buy out clause set at a prohibitive £102m.
He is open to a Premier League move but Chelsea would offer substantially less than his clause. They want to add five new signings this summer with centre-backs and full-back the priority for Thomas Tuchel.
The German manager will look for defensive reinforcements after Antonio Rudiger and Andreas Christensen both departed the club on free transfers to Real Madrid and Barcelona respectively.