Aberdeen boss Craig Brown is worried the club will lose Zander Diamond after Hearts stepped up their interest in the defender.
Diamond is out of contract at the end of the season and Hearts have been in touch with their SPL rivals to register their interest.
The 26-year-old has yet to hold talks over a move to Tynecastle, but Brown is aware that Aberdeen are unable to compete financially with Hearts.
Brown said: "The fax makes it clear we now have a fight on our hands to hold on to Zander. If it comes down to straight finances then he will probably go to Hearts.
"They can afford to offer Zander double the basic wage he is likely to get with Aberdeen. I told Zander about the fax and asked him to let us know if Hearts follow it up by opening talks with him.
"He hasn't come back so far but it looks as if it's only a matter of time before they offer Zander something.
"I appreciate the way Jim Jefferies has kept us informed right down the line but it's a worry that we could lose Zander, who is a key player at Pittodrie."