We've got enough cover now if nobody is sold I reckon.
At right back we have Valencia, Darmian, Jones and even Smalling plus Lindelof can also cover there.
Centre Back we have Bailly, Jones, Smalling, Lindelof, Blind as cover and Rojo to come back.
Left back we have Blind, Darmian, Shaw hopefully proving the best option (we should know by the next transfer window so I'd use that one if needed not this one) and *shudder* Rojo coming back as cover. Even Young can cover.
That's without the younger options so I can't really see the need to add defensively unless you are replacing someone with a new first choice player which is a different thing altogether.