In-form front-rower Justin Poore will be out until the semi-finals after suffering a dislocated kneecap in the rugged 13-12 loss to Cronulla on Saturday night.

Scans on the 23-year-old injured prop's knee yesterday revealed he will miss between four and six weeks. He will undergo arthroscopic surgery this week.

Adding to the Dragons' woes, fullback Brett Morris will miss a week after damaging his left shoulder in the loss to the Sharks.

Dragons officials said injured veterans Mark Gasnier (hamstring) and Jason Ryles (thigh) would also miss the crucial game against the red-hot Tigers.

The bad news comes after a strained quadricep had already ruled out international back-rower Ben Creagh for over a month.

The run of injuries has come at the worst possible time for the Dragons, who have gone from fighting for a place in the top four to fighting for a spot in the finals after losing two of their past three games.

With six sides within two points of the Dragons on the ladder, including the Tigers, this Friday night's game shapes as the most important of the season for St George Illawarra.