Penrith will be forced to drop one of the stars of their resurgence, fullback Matt Moylan, because of what officials have called ''unreasonable'' second-tier salary cap restrictions.

The Panthers have been notified by the NRL that should they play Moylan against Wests Tigers on Sunday, they will risk a substantial fine, and there are also doubts about winger Travis Robinson's availability for the match.

Thrown back to the Wolves: Promising fullback Matt Moylan has been forced to return to NSW Cup. Credit:Getty Images

Moylan is said to be ''shattered'' by the development. His manager Allan Gainey said he would likely consult with lawyers over whether the move was a restraint of trade. Instead of playing in the NRL on Sunday, Moylan is likely to turn out for Windsor Wolves against Newtown in Parkes on the same day. Robinson's selection will need to be confirmed by further discussions.

Moylan and Robinson were called into the side in round seven as the club dealt with a shocking injury toll. The pair have since played a key role in the Panthers winning four of their past five matches, a run that has moved them into the top eight.