St George Illawarra players Ben Creagh, Brett Morris, Trent Merrin and Beau Scott have missed out on selection for two upcoming Australian Tests because of post-season surgeries.
The Dragons quartet was among nine players to withdraw from the final 18-man group to play Papua New Guinea on September 23, after being selected for the initial training squad.
Mitchell Pearce, Jake Friend (Roosters), Robbie Farah (Wests Tigers), Tim Grant and Luke Lewis (Panthers) have also been made unavailable because they're due to undergo post-season procedures.
Dragons performance director Andrew Gray said both the Port Moresby game and subsequent end-of-season Test against New Zealand at Townsville fell at a bad time for the players, who will all undergo surgery in the coming weeks.
"Trent Merrin will undergo ankle arthroscope to repair damage sustained earlier in the year," Gray said.
"He will require corrective surgery as he has been carrying it for the majority of the second half of the season.
"Furthermore, Ben Creagh will undergo an arthroscope to repair damage done to his shoulder which he also sustained earlier in the season.
"Brett Morris has had ongoing back and hamstring problems that we have investigated and we plan to go ahead with the required relevant treatment and subsequent protocol. This program will render Brett unfit to train for at least three to four weeks.
"Beau Scott will undergo groin surgery."
The Prime Minister's XIII to play Papua New Guinea will assemble at Allianz Stadium today for team medicals, before departing Sydney on September 20.
Meanwhile, Justin Hodges, Sam Thaiday, Paul Gallen, Wade Graham, Bryce Gibbs, Greg Bird and Nate Myles have been selected for the Test against New Zealand on October 13.
Further players will be added to the train-on squad for the New Zealand Test as teams are eliminated from the NRL finals.