Unai Emery, manager of Villa, revealed that they must sell players before they can reinforce their squad in January.
"We have to accept the rules and accept that if we want to sign someone, one has to leave on our list in the squad," Emery said.
"For financial fair play, we will need to accept the rules and how we are. They (the owners) want to invest more and more but accept the rules and accept financial fair play. We are trying to be intelligent in our transfer windows. We are trying to improve our squad with some players and if we can't do it now, we can think of the next transfer window in the summer."