Sydney FC coach Graham Arnold has confirmed that Alex Brosque will be on the sidelines for up to a month due to a hamstring injury.

Brosque suffered the injury against the Jets in round nine, before returning to the side for Sydney's Boxing Day clash against the Mariners.

However, he only lasted half an hour before re-injuring his hamstring, forcing him off the field, which will now force him out for three to four weeks.

“We didn't bring him back too early, he got misdiagnosed with his scan,” Arnold said.

“He trained a full week before the Mariners game, he wasn't feeling anything then 25 minutes into the game he felt it.

“It's a blow to lose your captain but I was very happy with what George Blackwood did last week. We hope to have him back for the start of the Asian Champions League.”

Sydney face Newcastle this Saturday afternoon at ANZ Stadium.