Preparations for Sydney FC's Asian Champions League campaign have begun in earnest with coach Graham Arnold already working the phones for January's transfer window.

Last year's A-League grand finalists' first game in Asia isn't until February 25, however Arnold said the club has already started looking for reinforcements before their schedule tightens significantly.

"I'll just say the phones have been working hot. That's what the January transfer window's for," Arnold said.

"Whether it's rebuilding, restarting, or strengthening, some players that may not be getting game time here want to get game time and want to move on.

"It's also about bringing players in to strengthen the team for the second half of the season."

The Sky Blue were active participants in last year's window, netting French-Senegalese pair Mickael Tavares and Jacques Faty, both of whom went on to play in the grand final defeat to Melbourne Victory.

That was after they lost then captain Sasa Ognenovski and Corey Gamiero to long-term injuries just before Christmas.

This year, hamstrung skipper Alex Brosque is the only injury concern on Arnold's roster ahead of Saturday's clash with Melbourne City, however a gruelling six-week period looms.

Between February 20 and April 6, Sydney play a total of 11 games, including a heavyweight meeting with Chinese giants Guangzhou Evergrande.

One problem for Arnold, who twice took the Mariners to Asia between 2012-14, is a full compliment of five foreign players currently in the squad.

Teams can only have three on the their ACL roster, due to be named later this month, plus a fourth from an Asian Football Confederation nation.

"That's where I'll try to see with my contacts and network of agents, of what's available out there and what we can do in the second half of the season," Arnold said.

"It's no secret that we got Asian Champions League (coming up).

"We've got more than enough Australian players here, and we've got the full quota of five foreigners as well. But we can explore maybe the guest player option as well."

The transfer window begins on January 14 and is only open for a month.