THE knee was sore alright but didn’t feel as if it was a serious injury. At least that’s what Daniel Arzani thought at the time.

He hadn’t long come on as a substitute at Dens Park, on Halloween last year of all nights, having had to wait (im)patiently to make his Celtic debut, but the Australian lasted just twenty minutes before twisting his knee.

Arzani had been awarded a hero’s welcome when Brendan Rodgers put him on before the hour, with Celtic coasting to a 5-0 win, and showed some lovely touches in his brief appearance, hinting that he could live up to the hype which surrounded his signing.

Indeed, so confident was the player he wasn’t badly hurt, he gave the Celtic supporters a wave with both hands as he was taken off the field by stretcher. After all, he’d be back in no time. Bit of ice and some magic sponge would get him right as rain. Why feel too down even if this wasn’t how the evening was supposed to end.

Just 24 hours after his debut, the 20-year-old was told his season was over. His ACL was done. There would be no quick way back.

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Arzani was all smiles at Celtic’s training centre yesterday. But his troubles aren’t over.

That’s eight months since he’s kicked a ball. He hopes to be training with his team-mates later this month. However, it might be a couple of months before the supporters get to cheer his name again.

That’s the thing when a football does their knee in this fashion. The rehabilitation takes as long as it takes. Rush and it could be career threatening.

“It was gut-wrenching,” admits Arzani when asked to go back to that night on Tayside. “I didn’t actually realise I’d done my ACL at the time. It wasn’t like it was a big impact or anything.

“It just shows how precarious football can be. One minute you are on a high after the World Cup, singing for Manchester City, going to Celtic (on loan for two season), then, boom, an ACL injury. It was a huge setback.”

That’s an understatement. It’s also serves as a reminder about the fragility of a football career. Arzani was on cloud nine. Then one twist – it looked nothing at the time – and he couldn’t walk.

“The night had been really good,” he said. “I don’t know if you recall but I was clapping the fans as I was coming off. That was because I didn’t actually believe I had done my knee. I was buzzing. I was really happy. I was thinking ‘it’s OK, in another couple of days I’ll be alright’.

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“I was in great pain but I had heard that when you do your ACL sometimes you don’t get any pain. So I thought it was something else. I had been told before that, sometimes with ACLs, people continue playing because it’s not too bad. But for me it was really bad.”

Arzani comes across as a level-headed young man, which helped when faced with such a long time out.

He spoke to other players who had gone through the same as he diligently put in the hours in Glasgow, Manchester and Barcelona where he a top surgeon put his knee back together. The next bit might not be for the squeamish.

“The surgeon’s work is about 95 percent with footballers. Most of the Spanish players go to him (Dr Ramon Cugat). He helped the likes of Benjamin Mendy and Kevin de Bruyne, plus Fernando Torres. His wall is full of autographs and pictures and that gives you confidence.

“When you see those names and pictures and all of the players who have got back playing again, he must be very good at what he does.

“Speaking to the physios here, ACL injuries used to be career threatening. It’s a lot more straight forward now. You’re out for the rest of the season or longer considering when you do it but it’s definitely not as bad as it once was.

“You can get a hamstring or a patella graft and I got a patella graft. That’s supposed to be a little bit stronger in the long term but I don’t think that’s 100 per cent confirmed.

“You do 10 times more work when you’re injured. It’s ridiculous. You come in in the morning and there is so much to get through. You’re leaving every day at four of five so you are actually staying back later because you are not training with the boys. You’ve got to be in the gym doing this and that. Then you’re in the pool and you are back out again. There is so much stuff to do.”

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“At least he can see the end of what must have been at times the longest tunnel. It just won’t happen tomorrow.

“I’m not quite ready,” he admitted. “I’m going to be on my own doing rehab this week. Then next week, when the boys go to Austria, I’m going to Manchester to do my final tests to see that everything is matching up in both legs. If everything goes to plan, hopefully after that I’ll be training.

“At the moment, with where my heads at, I’m just focusing on getting my body right now, feeling good again, feeling that I’m not scared about changing direction or anything. I just want to play. I’ll focus on that after.

“I just want that one full game first. Firstly, I need to get back into training and so well and having the gaffer’s faith in me to put me on.”

Arzani could do with a bit of luck and Celtic need a player capable of lighting up a game on a drab day.

He’s had to be patient but his tolerance levels have peaked.

“The Scottish Cup final with Hearts is a game which stood out for me,” he said. “It was just one of those ones where it was a bit of a grind. It wasn’t a pretty game but we got through it.

“We all went out on the field and had the cup. It was just a great feeling. I remember walking out onto the field after the game and just thinking that I want to be a part of it.

“I was a part of it but I wasn’t playing or there day-in, day-out. I really want that feeling”

It’s the least this unlucky young man deserves.