Sydney FC midfielder Nick Carle will be sidelined for another four weeks with yet another injury.

The former Crystal Palace man had already been out of action for a number of weeks with a foot injury but will now miss a further month because of a back complaint.

Carle has only managed seven appearances for the Sky Blues this season and admits his return to Australia has been very frustrating.

"I just want to be out there with the boys. I am a footballer so not playing hurts," Carle said.

"We have such a great bunch of blokes here so not to be out there with them week in, week out is really tough. I will be positive and stick to the program the club's staff will set out for me and come back from this."