LUCKLESS Sydney Swans defender Alex Johnson says he's determined to resurrect his career, despite the chance he will never play again after he undergoes a fourth knee reconstruction.

Johnson, who has not played since the 2012 Grand Final triumph, has already been ruled out of the upcoming season. 

The 22-year-old is set to undergo a bone graft operation in March to prepare him for his next reconstruction.

"I've got my sights set on playing again, but when that will be I'm not too sure," Johnson told the club's website. 

"That keeps me going, and that's a massive driving factor behind my rehab and my positive attitude.

"Nothing can prepare you for an injury like this … but keeping a positive mindset is really important for me and I'm just looking forward to getting back and playing."

Johnson first ruptured his ACL in 2013. Infections have undermined his recovery from three subsequent reconstructions – one traditional and two LARS operations.

While his teammates were in the midst of last season's finals series, surgeons removed the LARS graft he had inserted last July.

"When you do an ACL you think you're most likely to miss one year, but one year has turned into two pretty quickly and it looks like it's going to turn into three," he said.  

"This time around we've had a few goes at it and it hasn't worked, so we just want to take the most cautious approach and make sure we 100 per cent get on top of it."

The support of family, friends and the Swans, plus the chance to get away to last year's World Cup in Brazil, have helped Johnson maintain a positive mindset.

On antibiotics for the next month, he has focused on building strength in his quadriceps and hamstrings to give his knee the best chance of recovering. 

The premiership defender said he was lucky to have support all around him as he recovers.

"John (Longmire) has been really good – he knows what a knee reco can do to a player as he’s been through a couple himself," he said.

"'Horse' and my line coach John Blakey have been really good and really supportive … and all of the boys, in particular Rhyce Shaw.

"He’s always kept really positive and made sure I’m still in touch with the group and that type of thing.

"To have someone like that on my side is really important for me and keeps me involved and keeps my mindset positive as well."