Gasnier suffered the injury playing his first game at stand-off

Gasnier was forced out of the St George Illawarra Dragons' game against South Sydney clutching his shoulder after coming off second-best in a tackle.

"I'm absolutely shattered, I can't believe it. But I'll work hard to return as soon as possible," he said.

Dragons coach Nathan Brown described the injury as "a tragedy".

"He's one of the world's better players," Brown added. "But it's a rough game and we're not going to be the only club that goes through it.

"In the past we've shown when we've lost key players that we can still go well."