Solorzano, 23, was a key part of the club's last season, scoring 11 goals in 25 appearances.

But the striker's one-year loan deal from Costa Rican club LD Alajuelense has now expired.

Rival A-League club Melbourne Heart are believed to be interested in Solorzano and willing to buy him outright from Alajuelense, with the Costa Rican club likely to accept the best offer.

Solorzano previously had stated he wants to stay at Brisbane, but Postecoglou said it won't be easy keeping him.

"We might have a battle on our hands to hang on to him,” Postecoglou told The Courier Mail.