IT was not a night that anyone connected with Celtic will care to remember. But if they don’t face the facts of what happened to them in the Estadio Metropolitano on Tuesday evening, then it will have been a futile endeavour in every conceivable way.

That is the opinion of a still slightly punch-drunk Alistair Johnston, who was dazed by the experience of what Atletico Madrid did to him and his teammates, particularly after they went down to 10 men with the dismissal of Daizen Maeda.

They were already a goal behind by that stage, but the rampant La Liga outfit stuck a further five past Joe Hart, and Johnston is candid enough to accept that even the 6-0 scoreline probably flattered his team a bit.

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Unacceptable. Passive. Just some of the adjectives he used to describe Celtic’s performance, and ones that fans never want to hear.

It was, he says, the most chastening experience of his entire career to date, with Diego Simeone’s men able to toy with the Scottish champions, barely allowing them a kick as they desperately tried to keep the damage to a barely respectable level.

The opponents, he concedes, were on another level. But those Celtic players must now embrace a period of introspection to reflect upon their own individual roles in a humiliating evening, and a thorough examination of where they collectively have to be much better.

“It was the toughest defeat in my time at Celtic, for sure,” Johnston said.

“But in my career, I’ve never had a game like that, where they are just doing whatever they want to you.

“It was frustrating, difficult, because you it feels like you can’t get the ball, you can’t get in their half and it’s wave after wave.

“That is something we were so disappointed with. Even going down to 10 men, we should not have conceded that much territory and chances.

“We need to look at ourselves in the mirror, individually and collectively and figure out what we want to do – because that was unacceptable.

“If you don’t take anything away from it, then it really was a wasted night. Win or lose, you have take something from every game to grow as a group.

“This was a really talented group [we were playing against], they have World Cup winners in there and they really punished us.

“You could all see what the level is between ourselves and a team that is aiming to win the tournament, never mind get out of the group.

“For us, we have to look at it and realise there were levels, but there was also things, easy mistakes we made, that we can clean up.

“We know we have to be perfect – or near perfect – to get a result against these teams. Of course, if you go down to 10 you are really putting yourself behind the eight ball.

“Unfortunately it wasn’t the first time we’ve done that in this campaign. We’ve made it difficult for ourselves. But we played with nine men at Feyenoord for 25 minutes and looked more solid.

“It was a longer period in Madrid but we make it too easy. We were too passive. That was the frustrating part. We could have showed more with 10 men.

“Of course, you might not score three and turn it around, but we could have dug our heels in a bit more.”

Of all the Celtic players who were crestfallen by the manner of their defeat, none were more upset than Maeda himself, who had his shirt over his head as he trudged down the tunnel following the intervention of VAR, leaving his teammates in the trenches.

“Daizen was distraught,” Johnston said.

“It was a difficult one for him. He played on that edge, but he needs that edge. He is constantly pressing and running into tackles.

“That is what makes him so effective. In Europe it is reffed a bit differently, so I think that is something we are going to have to look at.

“But we need him to play with that edge, so we can’t take that away from him.

“It was frustrating for him and for us, and it made it a difficult night against a team I expect to go far in this tournament.”

The chances of Celtic progressing in the tournament are now infinitesimal, but where there is life, there is hope. They travel to Rome next to face Lazio, remarkably still having an opportunity to at least stay alive in European competition despite only picking up one point from their first four games.

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For Johnston, the final two group stage matches will be about showing how they have healed from their nightmare in Madrid, rather than allowing it to scar them.

“There is still something to play for in this group,” he said.

“We have put a lot of pressure on ourselves to get, not just a result, but three points against Lazio in the next match. If we can do that, we give ourselves a chance.

“We are in a difficult position, but I don’t see it as scars. We have the leadership in this team to put it behind us. But we do need to take something positive from Rome.

“Every single match we have had so far, we’ve felt we were in the games. Feyenoord, we went down to 10 and then nine, but we had moments in that game.

“Lazio at home we went toe-to-toe but gave it away at the end. Atletico, was a special night for everyone and a moment we need to hold on to.

“I believe on our day and if we play a perfect game – which we know we can do – we can go toe-to-toe with any of these teams.

“That is the frustration after picking up just one point in these four games.

“You have to be clinical and ruthless. We have struggled with that in both boxes.”