JONATHON Patton's teammates have seen him go through it before, but that didn't lessen the shock when the Greater Western Sydney big man ruptured his ACL last week.

Patton flew for a regulation mark at the Giants' main training session ahead of Sunday's clash with West Coast in Perth, but his left knee buckled on landing and left his teammates looking on helplessly.

Scans revealed the worst possible news and Patton is set to have his third knee reconstruction – his first two coming in early 2013 and again later the very next season on the opposite leg – in Melbourne on Tuesday.

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GWS star Stephen Coniglio, the club's second pick at their first NAB AFL Draft in 2011 behind Patton and who is also his long-time housemate, told AFL.com.au that seeing the power forward clutching his knee in agony again was a terrible experience.

"It's a s--t thing to happen to anyone, let alone a bloke who has already done it twice before," he said.

"It was really tough for myself and 'Shawry' (former flatmate Heath Shaw) and those guys that are closest to him.

"I'm a Catholic boy and when something like that happens you get really upset and question why, and Jonny is probably thinking 'why does this keep happening to me?' as well.

"But like anything in life you've got to roll with the punches.

"You've just got to find ways to keep positive and make little targets for him to aim for, even if it seems like there's not much light at the end of the tunnel."

The injury was a massive blow for Patton, who only eight days earlier had spoken to AFL.com.au about embracing the responsibility of being the Giants' No.1 target in attack after Jeremy Cameron was handed a five-game ban for striking Brisbane's Harris Andrews.

Coniglio said Patton was starting to find some of his best form after being dropped to the NEAFL earlier in the season.

"With 'Jezz' going down I thought it was an amazing opportunity for Jonny," he said.

"I had no doubt that he would have turned his form around and would have been that reliable big forward that we expect him to be, and he expects himself to be.

"But he's being very optimistic about his return and I've got no doubt that he can come back and be a great power forward of the competition.

"He's been really positive about coming back bigger and better."

GWS head of athletic performance David Joyce told the club website that Dr Julian Feller will perform Patton's surgery once swelling around the knee has subsided, after working on the Giant with his previous ACL operations.

"We'll probably use what’s called a quads tendon - so the tendon on the top of the kneecap - and we may do some reinforcement of it as well," he said. 

"We expect him to be in Melbourne for a little bit after the surgery and then he’ll recommence his rehab process with us."