A-League club Melbourne Victory are determined not to lose Socceroo Mark Milligan for anything less than top dollar - and would prefer not to lose him at all.
English Premier League side Crystal Palace have confirmed they are chasing Milligan, and the Victory say they have submitted an offer.
But the Victory say it is well below market value - believed to be around $A500,000 with add-ons.
Postecoglou says Milligan is the best player in Australia right now, and doesn't want to sell a player central to his A-League plans.
"We haven't got a `for sale' sign up. If somebody knocks on your door, and says I want your house, do you give them a price? Or do you tell them what you want?" Postecoglou said on Monday.
"We value him very, very highly ... we'd expect them to meet our valuation of him.
"He's the best player at our club, he's the best player in the country at the moment.
"I don't think we need to be out there trying to flog him, and we're certainly not doing it for the money."
Milligan has a further two years remaining on his Victory contract, meaning the club does hold the whiphand in any negotiations.
If the 28-year-old does leave the Victory, it would leave a massive gap for the club to fill for the A-League season starting in October.
Already the Victory have sold midfielder Billy Celeski to the Middle East, and after the departures of Marco Rojas and Marcos Flores in the off-season, they can ill afford to lose a player of Milligan's quality.