WESTERN Bulldogs rookie Roarke Smith is remaining upbeat despite suffering the second serious knee injury of his career against the Brisbane Lions at Etihad Stadium on Thursday night.

Scans on Friday confirmed the devastating news that the 20-year-old had torn the anterior cruciate ligament in his left knee.

The defender will undergo a traditional knee reconstruction, Bulldogs physiotherapist Chris Bell announced.

Smith, who has played two senior games in his three-year career, ruptured the ACL in his right knee in the VFL finals in 2015.

"It's a long recovery but hopefully it's not as long as the last one and I'll try to get back for finals or whatever," Smith told reporters on Friday. 

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Smith said he knew he was in trouble as soon as he suffered the knee injury in the third term.

"I sort of knew. It was the same as the last knee. There was a pop and it feels a bit empty, but we'll get the scans and see what happens."

But he is taking confidence from the way teammates Clay Smith, who has recovered from three ACL injuries, Jack Redpath and skipper Bob Murphy have rehabilitated from their serious knee injuries. 

Geelong's Daniel Menzel is back playing after four knee reconstructions, including a LARS procedure. 

"People do knees and they come back. Menzel's done four, look at him now, he's killing it," Smith said.

The young defender said the support he had received had been overwhelming, highlighting the backing of his captain. 

"Bob's always there. Even with my first knee (injury) he was always there to give me guidance and he helped me through the whole way," he said. 

"But then again, the whole club did and they're really supportive.

"The boys are really supportive, all the staff and all the fans get you back on your feet and keep you positive.

"It's a good club to be at, that's for sure."

Smith comes out of contract at the end of 2017, but coach Luke Beveridge said the club would care for the defender through his latest injury setback.

"We will support him and get him going again. It's a bitter pill to swallow," Beveridge said. 

"We think Roarke has a really bright future. It's just a shame he has had so much bad luck so early in his career."