The St George Illawarra Dragons have confirmed second-rower Jadyn Su'A will play again this year despite suffering a knee injury last weekend against the North Queensland Cowboys.

The State of Origin calibre edge forward has been one of the best in an underperforming St George Illawarra side this year, but has now been added to the club's lengthy injury list which also features a host of players out for the remainder of the year.

Su'A though will be back before the end of the campaign which is unlikely to bear a finals appearance for Shane Flanagan's side after losing the last four games on the trot, despite being in a position to win the majority.

His Grade 2 medial ligament injury will see him avoid surgery and be in line for a return in Round 25.

That means he will miss this weekend's game against the Canberra Raiders, where he has been replaced by Michael Molo, as well as a local derby in Round 23 against the Cronulla Sharks at Kogarah, and a Round 24 trip to Auckland for a game against the suddenly struggling New Zealand Warriors.

He should be fit to return in Round 25 against the South Sydney Rabbitohs, who themselves have a long injury list, and will now need to fight to avoid the wooden spoon without Jack Wighton who has been suspended for the next four weeks.

The news is worse elsewhere for the Dragons, with the joint-venture confirming prop Toby Couchman will undergo shoulder surgery, ending his season, while young winger Sione Finau faces the same fate.

Youngster Nick Tsougranis is yet to have a return to play timeline established after suffering a syndesmosis injury in the NSW Cup last weekend against Newtown, but he is unlikely to be back this year.

The trio, now out for the season, join a host of others sidelined at the Dragons, led by Valentine Holmes, Dylan Egan and Ryan Couchman.