Frustrated Sydney FC officials claim the only reason Graham Arnold overlooked them to stay with Central Coast is because they refused to accept a series of ''last minute'' demands.

The former Socceroos coach yesterday turned his back on an offer from his home-town club to fulfil the final year of his existing contract with the Mariners.

To add to the Sky Blues' dismay, it's believed the man once groomed for the Sydney FC top job, former captain Tony Popovic, will soon be unveiled as the inaugural coach of the new western Sydney club.

Popovic flew into Sydney last night to finalise terms with the club and it appears he will sign Ante Milicic as his assistant - after he was surprisingly overlooked for the Melbourne Heart job, where he has been assistant coach.

Fellow former Socceroo John Aloisi, who was also an assistant under John van't Schip, is expected to be unveiled this morning as Heart's coach.

That sequence of events potentially leaves Sydney as the only A-League club still without a coach, something it is clearly unhappy about given that the race to sign players for next season is already well under way.

Sky Blues' football director Gary Cole issued a statement yesterday registering the club's disappointment at the perceived U-turn from Arnold.

''Sydney FC presented a very attractive offer to Graham based on the understanding that he was free to join the club. We thought our offer gave everyone the best opportunity to come to terms,'' he said.

''We had asked Graham for a final answer by today but we were presented with some last minute requests, which we were not prepared to meet.''

Cole said the club would now turn to plan B.

Although it is thought even its back-up plan will require re-working now that Gary van Egmond has resumed his position at the helm of the Newcastle Jets.

''We have been working on a small number of alternative options for the head coach role,'' Cole said.

Cole's broadside at Arnold arrived shortly after the coach praised Cole for being ''extremely professional, understanding and respectful throughout this process''.

Arnold, 48, said the reason for his extension with the Mariners was because he couldn't make a decision as quickly as Sydney wanted.

''Sydney gave me a deadline and I couldn't meet the deadline,'' he said.

''In the end I would have had to break my contract with Mariners to join Sydney and I wasn't willing to do that.

''Now my aim is to replicate what we did this year.''

Arnold added that the prospect of competing in the Asian Champions League was a big lure.