Willie Miller brokered the exciting partnership with the Spanish outfit who will receive a percentage of any stars sold on by the Dons.
McGhee, who has struggled to bring in new players because of financial restrictions, said: "The tie-up came about from a contact Willie had at Espanyol who said they wanted to send a couple of players over and start a relationship with ourselves.
"Espanyol said they would make it easier for us to sign their players if we wanted to.
"We hope this will be an ongoing relationship and it has been a really positive start."
On Grassi, McGhee added: "The deal has to be financially right for us regarding Grassi but it looks as though that will be the case. He'll get a contract and as well as being physically right, he's a good player."