It was such a bad injury, a team-mate covered his face in horror when he looked down on James McPake lying stricken on the Dens Park pitch.
The big defender had suffered the damage as he made a whole-hearted challenge on John Rankin during the derby with Dundee United on the 2nd of January, 2016.
McPake candidly confesses that as soon as he was taken to the ambulance before being rushed to Ninewells Hospital, he knew his playing career could be over.
However, he fought the good fight and with the club’s firm backing, tried for two years to make a full recovery.
It was not to be and although the 35-year-old insists the whole experience is something he would not like to ever go through again, in all likelihood he wouldn’t now be preparing for another derby – this time as Dundee manager – if the injury hadn’t happened.
McPake said: “When I got injured in that derby in 2016 I knew straight away how bad it was.
“Within 10 minutes I was in the ambulance and I knew my career was over.
“I couldn’t straighten my leg and I could see how much damage there had been.
“I’d had bad injuries before but nothing as shocking and severe as that.
“The physio had told me to lie down and get it dealt with, and I also saw the reaction of the players.
“Paul McGowan and Nick Ross had come over and I can’t remember which one of them it was, but they turned away and covered their face.
“The pain was there but you are in so much shock.
“I was able to watch it back afterwards. I wanted to see it and see what happened.
“I have heard a lot of people say they can’t watch it back, but I had to – maybe I’m just weird that way.
“I was never going to admit that my career was over but I knew.”
McPake battled bravely to make a comeback enduring several operations and months of rehab but ultimately he had to admit defeat.
He added: “I came close to coming back but I think that was more to do with me telling myself I could come back rather than it being a reality.
“In the end you have to call time, because I realised I was probably doing it for the wrong reasons.
“When you are trying to come back to prove it to yourself it’s not right.
“I had a lot of long days and mentally it was tough, but I believe those times do make you stronger.
“There are people out there in much worse situations.
“It was annoying and hard, but it was not being able to do your job and you just have to remember there are people with illnesses who are far worse off than you.
“I look at it positively because if that injury hadn’t happened I wouldn’t be sitting here now preparing a team to go to Tannadice.
“I would have kept playing. I was still in decent condition, so things would be different right now.
“I would never say it was a blessing in disguise because I’d never want to go through that again.
“It was the hardest time I’ve had in football for me and my family, but it helped me get a head start in coaching and set me on the way to becoming manager of this football club.”
Dundee left no stone unturned in their quest to help the former defender and McPake admits he will never be able to repay the club for what they did for him.
He added: “What happened grew my affinity with the club because they were first class.
“I know the money the club spent on me, time and time again sending me to get treatment.
“They sent me to London five weeks in a row for injections – two people down to London, their food and hotels as well as the cost of the treatment. I had four surgeries as well.
“I remember John Nelms (club managing director) coming to see me when I was injured, my mum was there with us and he said whatever it takes, we’ll do it.
“I wondered if that was real but two years down the line I was still going to the best surgeons trying to get back.
“If it wasn’t for John and (physio) Gerry Docherty at this club I wouldn’t be able to walk without a limp, never mind kick a ball around with the lads here.
“I trained a little bit today with them, just kicked a few balls but all that’s down to what the club did for me.
“There will never be a way I can repay this football club for what it did for me.”
McPake will forever be remembered by Dundee fans for a derby goal he scored at Tannadice in August, 2015.
The Dark Blues were 2-0 down with just nine minutes left when Greg Stewart pulled one back before McPake popped up with a dramatic injury-time equaliser.
However, he insists another derby goal he scored is his favourite, from April that same year at Dens.
He said: “My best goal in the derby was the one here when we beat United for the first time in 11 years.
“We won 3-1. It was a big night for our fans and for the club because it had been so long.
“That was my favourite goal for the club.
“I think that was better than the equaliser down the road, although I celebrated that one in the same way.
“I know why everyone loved the game down there because we were 2-0 down and came back, but the win at home for me was a great one.”