Chelsea are in talks to sign Jorrel Hato from Ajax and have also held discussions over the signing of RB Leipzig's Xavi Simons.
Ajax defender Hato is one of a number of centre-backs they have been looking at.
Meanwhile, attacking midfielder Simons - another player Chelsea have held talks over - is set to leave RB Leipzig this summer as he has two years left on his contract.
Chelsea have other targets as well and any more incomings are dependent on players also leaving.
Simons is in demand and may wait until later in the window before moving.