There was more than one reason for Ronny Deila to lock himself in a darkened room last Friday afternoon.

Away from the mayhem, noise and electricity of last Thursday night's drama inside a heaving Celtic Park, Deila sought serenity in his Lennoxtown surroundings.

And then, finally alone with his thoughts, he hunkered down to watch a re-run of the Europa League game against Inter Milan.

Some of what he saw made him cover his eyes.

Other aspects of an unpredictable, tumultuous 90 minutes allowed him a quiet degree of tentative, cautious optimism ahead of Celtic's journey to Milan tomorrow morning.

"I sat and watched it over again and I have seen positives in our play," he said. "Against a good team we created opportunities.

"I think we will create opportunities over there. Defensively we have things we really need to work on and we need to be far more compact but I have to say - I do think we have a chance.

"I am not saying it will be easy, we know that. But we have to take the positives from the first leg. Our concentration has to be better. We can improve on that. "

Rodrigo Palacio, Mauro Icardi and Xherdan Shaqiri did not crudely carve apart Deila's game plan and leave Celtic's system in tatters last week; rather, they clinically capitalised on unforced, unimagined errors. The kind of mistakes that a manager cannot legislate for.

Craig Gordon has been a giant of a player for Celtic this season. Indeed, as Deila pointed out, if it were not for the stopper Celtic would be kicking back and enjoying a Thursday night off this season.

Yet his mistake at the opening goal and his harrowing error of judgment for Milan's third gave Celtic a mountain to climb.

Amid the euphoria of Celtic 's twice pegging Milan back - and for all the talk that the Serie A side are not the giants they once were it ought to be remembered that this is a club who won the Champions League less than five years ago - John Guidetti's last-gasp dramatic goal was celebrated with wild abandon.

Celtic, down and out after just 14 minutes, had every right to feel they got the draw their play so merited.

But in the cold light of day, the sobering fact remains that they must now go to one of football's great football cathedrals and keep a clean sheet.

If repeated, the nervous apprehension that seemed to seize the team, particularly the back four, in those opening minutes against Milan could cost them their place in the last 16 of the Europa League knockout stages.

Virgil van Dijk and Jason Denayer have grown in reputation at Celtic. But they are young - 19 and 23 respectively - and utterly wet behind the ears when it comes to this level.

And while Deila expects them to cope with that pressure, he has warned them they cannot be star-struck.

"You cannot be overawed," he said. "You cannot afford to stand off them and give them too much respect.

"Even the players who haven't played in Champions League game for Celtic in previous seasons have played in some big matches for Celtic now and I don't think that there is any concern that they aren't ready for this level.

"They want to be the best and this is how you will get better - individually and as a team.

"We have to be open-minded. We need a lot of energy, a lot of concentration, a lot of motivation.

"This is a big chance for us too. Yes, it is not an easy challenge, but it is a chance to go out and earn one of the biggest results of your career.

"We have to do what we can to prepare as best as we possibly can. We will have a plan and a system and it will be different to the way we played at home."

In any case, it will surely take an effort of monumental proportions to come away unscathed from Milan.

In European away ties Celtic have been perennially porous for just over the last decade; twice they have kept clean sheets in their travels in the last 11 years from European games, excluding qualifying ties.

Similarly, out of all Scottish teams only Rangers can claim to have walked off Italian soil with a win.

Paul le Guen's side achieved that feat back in 20006 against Livorno, but Milan with all their domestic problems this season have regarded this tournament as their best chance to win an automatic place in the Uefa Champions League group stages next season.

They will feel that they have one foot already in the last 16 of the competition given the advantage the way goals rule affords them.

And while Deila will encourage his players to try and snatch any chances that come his way, he will not be naive in his quest to get a result in Milan.

Kris Commons is available having played on Saturday after recovering from a hamstring strain while James Forrest was also back into the fray at the weekend.

John Guidetti's rise in belief will have given Deila some thought while the experience of Efe Ambrose may also be something he takes into consideration.

"It will be hard to pick the team because there are a few players who have come back," said Deila.

"There is a lot to think about because we have a particular way we want to play the game and it is deciding who are the best players to fit into that system.

"We have a good squad here and we have to use it to our advantage.

When we get home we do not have long to prepare for the game against Aberdeen so it is important that we are able to use the whole squad."