Gallen is struggling to overcome a back complaint suffered at training.

The 35-year-old did not join team members on the bus to Canberra which departed Sydney at midday on Friday.

The NSW skipper is believed to have stayed in Sydney to continue his rehab in an effort to be passed fit for the semi-final.  

He will travel to the Nation’s Capital separately on Saturday ahead of the 5.30pm kick-off.

Cronulla are already considered outsiders by bookmakers for the clash against the in-form Green Machine.