Former Chelsea midfielder, Gustavo Poyet, wants his former club to sign Matthijs de Ligt from Juventus this summer.
Poyet said he would be worried if Chelsea starts pre-season without De Ligt.
De Ligt has been linked with a move to Chelsea this summer from Juventus.
Chelsea are keen to sign a new centre-back this summer, having sold Antonio Rudiger to Real Madrid, with Andreas Christensen also set to leave the Blues.
“The most important position Chelsea should be strengthening is in central defence,” Poyet told Lord Ping.
“De Ligt is an interesting player because when he left his previous club he went somewhere that he needed to improve tactically and dramatically to perform at that level.
“If he wants to move and Chelsea can afford him then he could be an interesting player for them. If Chelsea start pre-season without that top level centre-back, I will be worried.”