Espanyol GM Roger Guasch cannot guarantee keeping hold of Mario Hermoso this summer.
The former Real Madrid defender has been linked with Arsenal and PSG this week.
Guasch says: "Is Hermoso going to leave? Maybe Hermoso like Borja Iglesiais will leave or even stay.
"The important thing is that if a player leaves, he must be replaced by a player of similar level, as done with Gerard Moreno."
Real are also interested and boast a buyback option in the deal.