Fijian Bati hooker Apisai Koroisau will not feature for the Panthers in round 13 of NRL.

Koroisau is part of the New South Wales game one squad as an 18th man for the State of Origin.

Both 18th men for the Blues and Maroons will be ineligible to play for their clubs this week.

It comes as a blow to the NRL leaders, who face their toughest test this week without their Origin stars as they bid for an unthinkable unbeaten season.

The Panthers faces West Tigers on Friday at 9.55pm.

Meanwhile, round 13 starts on Thusrday with the Dragons taking on the Broncos at 9.50pm.