Celtic’s Ryan Christie admits he was left puzzled and frustrated after missing four key matches through Covid-19 protocol rules.

The midfielder had to self-isolate for 14 days after he and Arsenal defender Kieran Tierney were deemed to be close contacts of Scotland midfielder Stuart Armstrong, who tested positive for the virus while on international duty.

Christie was ruled out of Scotland’s three matches against Israel, Slovakia and Czech Republic and the Premiership defeat by Rangers at the weekend while Tierney, because of different rules in Scotland and England, was allowed to play for the Gunners against Manchester City after missing out for Steve Clarke’s side.

The Hoops player returned as a second-half substitute against AC Milan on Thursday and, ahead of the trip to Aberdeen on Sunday, recalled his time off with little fondness.

The 25-year-old said: “I feel good. It was nice to be back playing. It was a very frustrating two weeks to be sitting on the couch watching games you feel you should have been part of. I was obviously desperate to play in this game.

“If I had missed one more I think my head would have fallen off. I was tested maybe five or six times during the time and every time it came back negative.

“I know there is a so-called bedding in period for the virus but you need to wonder when it goes past common sense. How long does this go on before before it gets ridiculous?

“It’s a rule that can be looked at. I had to get my head round it the first few days and obviously it was frustrating because I was in the same boat as Kieran who then played for Arsenal at the weekend.

“Now it is about moving on from it and hopefully it doesn’t happen again.”

Christie, however, will go above and beyond the coronavirus protocols in the future.

He said: “It opened my eyes to not doing anything wrong but still being punished.

“You just have to be very wary, even if you are of following the guidelines, that you need to maybe go that extra step further so nobody can point the finger at you.

“I will certainly be more aware going forward that’s for sure.”