George Wardlaw will be out for up to three months due to a hamstring injury suffered at training.
"This is obviously disappointing for George as he has been very diligent with his physical conditioning since he's been at the club," Kangaroos football boss Todd Viney said.
"While there are a lot of variables at play with his recovery, George is an extremely diligent and professional athlete and we know he will be ticking every box in his rehabilitation to be back as soon as possible."