Director of football Garcia Pitarch has confirmed that Valencia must sell players in order to comply with the Financial Fair Play regulations.
Arsenal have already made contact to sign central defender Shkodran Mustafi and recent reports have claimed that the player has already agreed personal terms with the Gunners.
And Pitrach hinted that a central defender will probably be sacrificed this month to meet FFP regulations.
"We're above the FFP guidelines," Pitarch is quoted as saying by Metro.
"That's the reality, and as of today, the four players we've signed cannot be registered, meaning we need to reduce the cost in a significant manner to register the players and sign a centre-back, which is a priority in case one of the ones at our club leaves.
"Obviously, if they don't leave, we can't sign a new one not only because of financial restrictions, but also because it wouldn't be logical to have five or six centre-backs.
"We need to continue with a reduced budget, but if there's an exit, we need a new centre-back.
"Our capacity is very limited. We've signed one player on a free, one on a loan with a view to buy, Nani in good conditions and Medrán as well because Madrid allowed it and the player decided to do so."