Celtic boss Ange Postecoglou on his substitutions, measuring sticks and a tilt at Europa Conference League

The Aussie watched Celtic crash out of the Europa League and drop into the Europa Conference League after losing 3-2 to Bayer Leverkusen in the Bay Arena in Germany last night.

Celtic had taken a 2-1 lead in the match but was denied their first-ever European win on German soli after conceding two late goals in the last eight minutes as the Bundesliga side ran out group winners.

The 56-year-old admits that whilst Celtic are a work in progress and are not at the level of Bayer Leverkusen yet he hopes that the Glasgow club can make significant inroads in the Europa Conference League in order to prepare themselves for sterner European tests in the future.

Here are the key points he made to the press after Thursday night's 3-2 defeat by the Germans.

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On the game

"It is a tough one to take as we kind of hung in there and gave ourselves a chance to pull off a great result.

"Ultimately they are a good team and we just didn't sort of finish the game off in the way that we could have.

"They knocked us 4-0 at home and we gave them a fright here and hopefully next time that gap is even smaller.

"We just hung in there and we weren't able to control the game the way we wanted to because they have quality in their side and they are always a threat on the counter-attack. We had to be a bit wary about that.

"Joe (Hart) made some good saves and the back four did well to keep us in the game but we just couldn't hang on in the end.

"I was disappointed for the players as they put in a massive effort. The players showed great determination and resilience to keep working hard and tried not to get away from the way we wanted to play and we gave ourselves a chance of pulling off a great result but ultimately we couldn't hang on in the end as they got the two late goals which were disappointing."

Postecoglou is more or less admitting here that he was bitterly disappointed to lose this match, especially when Celtic were on the cusp of achieving a monumental result in Germany.

Having got themselves in front, the manager seems to feel that in terms of game management his side should have had enough nous to see the match out.

The fact remains, however, that defensive frailties came back to haunt his side once again. That Celtic have gone to both Spain and Germany in this group and netted five times yet failed to take home a solitary point tells its own story.

The manager is adamant that he won't deviate from his style of play and such decisions will ultimately be on him as a result. The Celtic players are clearly buying what the Aussie is selling but the club will look back on both away matches against Real Betis and Bayer Leverkusen and reflect on what might have been.

READ MORE: Celtic showed they've narrowed gap, the board must now help Ange Postecoglou close it - Sean Martin

On bridging the gap to the top European teams

"Credit to the players as Leverkusen are a fantastic team and we came to their backyard and we gave them a game.

"There is still a gap between us and them and that's what we need to bridge. In all our European games we have taken it to some very good opponents.

"We know there is a gap between us and the best and we will bridge that gap if we keep taking this approach whenever we play these teams.

"It is definitely disappointing for my players but at the same time, it’s a great learning tool for us in our development.

“We know we’re not at this level yet, but we came here tonight and we were determined to take it to a good opponent and I thought we did that."

This was supposed to be the game where Celtic measured themselves against a side that was a Champions League team in all bit name.

Postecoglou vowed to take the game to the Germans and Celtic did just that but they came up short again from a winning position. However, the Celtic manager clearly trusts the process and he is instilling that self-same belief in his players and the supporters.

There was much to enthuse about with Celtic's performance at the Bay Arena and they did give the Germans a right old scare.

If anything, Postecoglou and his side will learn from the fact that they ran teams such as Real Betis and Bayer Leverkusen so close in the away matches. The real proof of learning will be in the pudding and if Celtic can use both defeats against Betis and Leverkusen as some sort of template to keep improving and developing then they might just be in with a chance of succeeding and advancing to the latter stages of the Europa Conference League.

On his substitutions:

“It wasn’t so much that it went wrong. I think obviously they were coming at us and they have some real quality in their team.

“I just felt that we lost a little bit of our composure at the end and maybe there was some tiredness. Guys coming on didn’t have the impact we wanted because we had some opportunities to create something ourselves and our decision-making wasn’t great and we allowed the pressure to build upon us.

"Jota is going well. We took him off because he and James in the front three worked really hard.

“I felt we needed some extra energy particularly in the wide areas and we had two players on the bench to do that. I felt it was a good time to make the substitutions.

“You saw that he is playing against a very good team, good opponents, he wasn’t able to dominate the way he usually does. He just needs to keep working at it. He’s a young guy and he’s still learning.

“He took his goal really well, which again showed his quality but there are still a lot of areas he needs to develop and the more we push him to play the football we do the more he will develop. He wants to and he knows he still has a lot to learn.”

The manager uses this opportunity to defend his substitutions, which some fans were highly critical of after the match.

The bottom line is that the front three of Jota, Kyogo and James Forrest had all run their race. Nobody can dispute Postecoglou's logic in making the changes with less than 20 minutes left on the clock - although he may have kept the influential Jota on for longer as he looked capable of grabbing or creating a decisive third.

The problem here is that the threadbare nature of the squad means that Postecoglou was not replacing like for like. Even the Aussie cannot legislate for the likes of supposed impact subs such as Mikey Johnston, Albian Ajeti and Liel Abada not contributing to the cause and not impacting the game in a way he would have desired.

It may also have been a clever and subtle warning shot over the bow in order to say to the Celtic hierarchy that the squad is still badly in need of a quality overhaul in several key positions.

With January in mind, the $64,000 dollar question remains - how much backing will the Celtic board give Postecoglou in the January transfer window? The ball is most certainly in the court of Celtic's money men.

READ MORE: Celtic duo Jota and Kyogo's elite numbers make European trophy target feel realistic

On the Europa Conference League:

“My main thoughts are around how do we get to this level?  This is where we want to be. It’s not that we are disappointed we are in the Conference League, but we want to be competing at this level with these teams.

“I felt with all the group games we slowly became a better side at dealing with the best teams in this competition. How do we bridge that gap?

"I want us playing against the best in the best competitions. There is still a little gap there and we have to still build from that.

“The Conference will maybe give us an opportunity to play in different conditions against good teams. There is a lot at stake in European football.

"Can we still hold up and stand up against the best? That’s what’s important to me."

While Postecoglou does not want to be competing at the Europa Conference League level, he would gladly have taken a run to the knockout stages of this tournament back in June when he took over the managerial reigns of the club.

If Celtic are to continue their development and to be a Champions League-ready team come this summer then an extended run in Europe as well as reaching the latter stages of this inaugural competition could work wonders.

With the goal of competing against the best and featuring regularly at Europe's top table, they must learn to cope with the demands that will be placed upon them at this level first.

Postecoglou has set his heart on transforming Celtic both domestically and in Europe and making the Glasgow side a big noise abroad again. Every rebuilding process has setbacks and this may well be what the Hoops need to restore some levels of confidence on the European scene.

If Celtic can make a go of it and a fist of it in the Conference League, that vital experience will stand Postecoglou's men in good stead moving forward.