Three-four millimetres – the fine line between football and retirement for Linvoy Primus.
At the age of 34, the Pompey favourite is valiantly swimming against the current dragging him towards his career's end.
He has one final hope, one desperate grasp of the lifebelt.
And for the popular defender, it's a fight for footballing survival he has no intention of losing.
Primus' future has been placed in the hands of world-renowned knee specialist Dr Richard Steadman.
The American surgeon has already rescued the livelihoods of Michael Owen, Ruud van Nistelrooy, Alan Shearer, Roy Keane, Ronaldo and Craig Bellamy.
Now the Blues battler is following their example, becoming the latest to undergo Steadman's pioneering method of microfractures.
Involving drilling 3-4mm holes into the back of his problematic left knee, the delicate procedure allows bone marrow cells and blood to combine to form a super clot which completely covers the damaged area.
The anticipated result is expected to repair tissue inside the knee, with it back up fully functional between two and six months.
Success or failure – Primus has nothing to lose.
Without an appearance this season and with his contract expiring at the campaign's end, his footballing life is fading.
But there is no-one better than Steadman to resuscitate it.
Primus said: 'The operation is something a lot of athletes from all sorts of sport have undergone and the success rate is very high.
'There's a basketball player who has had both knees done, which is incredible.
'Their sport is obviously a bit different from ours but the aggression on their knees is far higher than what footballers have.
'Within a year of having both of his operated on he is playing regular basketball in America.
'Really for me that's a big thing, an inspiration in a way.
'I think to myself there is somebody who is putting a lot more force on his knee on a harder surface but is out there playing again.
'They also have footballers at the end of every season, one of the guys there was saying they have five or six come in for a microfracture every summer, it's a common problem.
'It was actually Harry who had mentioned him to me, he had also known about Dr Steadman through his son Jamie, who's had knee problems in the past.
'Basically it was a case of there being a problem, we needed to see what was going on and he's the best man for doing it.
'The microfracture process is a term used in America and it's used a lot more than here, but it's a common injury and it's a common operation.
'Basically a cartilage had worn away behind my kneecap so they perform microfractures which pick into the bone and encourage it to bleed to form new bone.
'Dr Steadman's happy with the way everything went and has said it's down to me now to do the right thing.'
Primus' left knee remains in a brace while he is still confined to crutches, following his operation last month.
Fighting his way back to footballing fitness is a long process and it remains touch and go whether he will play again this season.
Next month he will return to Steadman's Colorado base for a routine examination to gauge the recovery.
In the meantime, he follows a specific recovery programme aimed at keeping his rehabilitation on the right track.
All talk of playing for Pompey again remains on the backburner.
Instead recovery is the priority – no matter how long it takes.
He added: 'I'm good at the moment. The operation has been completed and I'm now at a crucial stage where I have to carry out to the letter everything Dr Steadman told me to do to enable it to recover as fully as it can and give me the chance to play again.
'The difference between success and failure is what you do afterwards in your rehabilitation, not necessarily the actual operation.
'I'm actually in the same position as I was following the operation in that I've still got my leg in a brace and still got minimal movement on my kneecap.
'As part of my physio, I spend six hours a day on the CPN machine which moves my leg back and forth and keeps my knee up to stimulate cartilage to grow.
'That's something I do at home. It's quite a tedious time but I know it's something I need to do to give me the best chance when I go back to see him in a few weeks.
'It means I'm watching a lot of films and reading a few books, but if I can play football again at the end of it, it is all worthwhile.'