St George Illawarra Dragons trio Josh Dugan, Brett Morris and Trent Merrin have all been ruled-out of the Australia Kangaroos train-on squad due to respective injuries.

All three Dragons players had originally been named in Australia Head Coach Tim Sheens’ initial train-on squad ahead of the Four Nations Tournament.

Dragons centre Josh Dugan sustained a thumb injury during the fixture against the Newcastle Knights in the final round of the regular NRL competition.

The NSW Blues representative has since had x-rays which have confirmed a small fracture in his thumb which has been immobilised in a splint.

Dugan will be required to wear the splint for at least the next four weeks and will be progress reviewed then.

Dragons duo Trent Merrin and Brett Morris will both undergo shoulder surgery later this week to correct respective shoulder injuries sustained during the State of Origin Series.

Dragons winger Brett Morris is expected to be side-lined for up to four months and is scheduled to commence his pre-season training in February.

The Kiama Knights junior initially suffered his injury while representing the NSW Blues in the first State of Origin fixture and was subsequently unavailable for seven weeks before returning against the Manly-Warringah Sea Eagles in round 19 and played on for the remainder of the season.

Additionally, lock Trent Merrin is likely to be side-lined for up to three months and expected to commence his pre-season training in January.

The Shellharbour Sharks junior additionally suffered his ailment while representing the NSW Blues in the third State of Origin fixture and was subsequently side-lined for a fortnight before returning against Wests Tigers in round 20 and was able to finish off the season.