For example would Thibaut Courtois be allowed to play for the Spanish side?
The Belgian stopper is currently on loan at the club for the third season in a row but the rules regarding loans domestically are often different for those out to the continent.
Secondly, a player largely regarded as their main transfer target would also be on the opposing side as Diego Costa would be lining up for Los Colchoneros.
The Brazilian born Spanish international has fired in the goals in the absence of Radamel Falcao - and earned rave reviews for doing so.
So when Diego Simeone, the Atletico manager, speaks about either player it will always, no doubt, be of interest to Chelsea fans.
Simeone has been speaking to Spanish radio about many things - including his two star players of whom he stated:
“Goalkeeping is very important for every team. I’d like Courtois to stay, he knows that. Costa’s going to provide the biggest boost to the Spanish team in Brazil. There’s no one like him.”
Jose Mourinho has been insistent on the matter of Courtois. He has no intention of selling the player however the goalkeeper also has some assurances that need sorting.
He wants regular first-team football - and will not be returning to Stamford Bridge to play second fiddle to Petr Cech.
On the topic of Costa it is a simple case of whether Chelsea want to stump up the cash for him.
He has a reported release clause of £32 million and Chelsea seem to have a need for strikers at the club for next season - especially as their star striker has been the veteran Samuel Eto’o.
It is a topic that will continue to cause mass interest among Chelsea fans - as next season could see one of, both or neither or these two top talents playing in West London.
Only time will tell.