With the Sky Blues seven points clear on top of the A-League ladder after a league record 13-match undefeated start Arnold on Friday reiterated his belief they could remain unbeaten for the whole season.

Arnold said his team were still only playing to around 60 per cent of their potential.

He tipped them to produce the best away performance of the season in Sunday's Gosford showdown with his former club Central Coast Mariners.

Centre back Jurman left this week for South Korean club Suwon Bluewings, but his departure, along with that of goalkeeper Vedran Janjetovic to Western Sydney, means Arnold has the resources to bolster his squad in the January transfer window.

"We've got a visa spot open, we've probably got at this moment 20 players put forward, current internationals for European nations," Arnold said.

"We've got money in the cap. With Janjetovic and Matty Jurman leaving it's opened up a good amount in the salary cap to bring in a top central defender if need be."

Arnold wouldn't disclose who the players offered to Sydney were, but suggested they weren't big names.

He had no immediate concerns about replacing Jurman, with experienced defender Seb Ryall set to move in alongside Alex Wilkinson on Sunday.

He also had no shortage of options to replace suspended skipper and leading scorer Alex Brosque.

"Bernie (Ibini) has come on, he's fit, he's ready. It's taken time to get to where he's at today," Arnold said

"David Carney has come back from a small calf (injury), but he's fine.

"George Blackwood is there as well, Matty Simon, so we've got plenty of depth in that department."

Arnold has been working on getting more out of his attack despite Sydney being the competition's leading scorers.

"The combinations in the front half of the field will get better and better. They are still not there," Arnold said.

Sydney's piled up four goals in each of their two most recent away games.

"The training sessions this week have gone up to another level and I'm expecting probably our best away performance this week," he said.