Sky Sports sources understand Chelsea's interest in Scott Dann depends on whether the Blues can get a work permit for Serbian defender Slobodan Rajkovic.
Rajkovic was signed by Chelsea from Serbian club OFK Belgrade in 2007 and has since been loaned out to Eredivisie outfits PSV Eindhoven, FC Twente and Vitesse Arnhem.
But he has returned to Stamford Bridge and played in the Blues' pre-season tour.
The 22-year-old is very highly rated by new Chelsea boss Andre Villas-Boas but he does not as yet have a UK work permit.
It is understood if the Blues manage to get one for him, they will not spend any more money on centre-halves.
However, if they fail to get the work permit, Birmingham ace Dann is one of two targets that the Stamford Bridge outfit are closely monitoring having studied DVDs of the player and watched him in pre-season.
Liverpool are also keeping a close eye on Dann - who was born on Merseyside and is a lifelong fan of the Reds - but it is understood they would need to off-load players first before making their interest formal.
A deal to take Dann to Stoke previosuly broke down because personal terms could not be agreed but it is understood that deal is not totally dead in the water yet.