Ange Postecoglou has faith in the Celtic 'process' as boss refuses to budge on principles - points from the presser

However, as Celtic boss, Ange Postecoglou watched on as his side sunk to the bottom of Group G table, the Aussie insisted that he was still going to persevere with his football philosophy and style in order to make his men a force to be reckoned with at home and abroad.

Despite registering just two wins from their last eight matches in all competitions, Celtic head to Pittodrie to face Aberdeen this Sunday. Without an away victory to their name this season, Ange is well aware this his side need to deliver in the Granite City. Just don't ask the 56-year-old to change his style of play. Ange just ain't entertaining that notion at all.

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Speaking to Broadcast, Ange was adamant that he would continue to do what he feels is right until his team get it right.

He said: "If you kind of accept it then you won't grow from it. When you lose 4-0 it's not enough.

"It is disappointing and that scoreline should not have reflected that game. I don't want to let the guys or myself off the hook. We are not going to change our approach.

"I really believe that moving forward when we play in these big games I want us to be a team that doesn't fear anyone and goes at it and takes the game to opponents who are quality sides.

"That's the kind of team we are going to be and that's what I am trying to build.

"The process takes time and we will cop some knocks on the chin (like we did tonight) but that doesn't mean you have to accept that and you need to understand that's avoidable if you do certain things."

There may be a sense of growing disgruntlement among the Celtic supporters and many of them had seen enough and headed for the exit signs shortly after the Germans made it 3-0. The line: "We are not going to change our approach", may well have jarred amongst many.

Similarly the phrase: "I really believe that moving forward when we play in these big games I want us to be a team that doesn't fear anyone and goes at it and takes the game to opponents who are quality sides. That's the kind of team we are going to be and that's what I am trying to build."

The biggest irony here is that it's actually Celtic who are the team that opponents no longer fear both at home and in Europe. Whatever Ange is doing clearly isn't working yet and that is manifesting itself in results. The Aussie remains defiant and is steadfastly sticking to his principles. The Celtic fans are perfectly entitled to ask Ange - at what cost?

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Those supporters still firmly entrenched in the pro-Ange camp are still trusting the process. However, as Ange explained to Celtic TV even those words are sounding more hollow as time goes on. He reminded the players that they have a duty to perform for their supporters starting against Aberdeen on Sunday.

He said: "The players cannot put this game to the back of their minds they have to put it to the front of their minds. We can't keep disappointing our supporters.

"We can't keep saying we've had disruptions and issues with the squad and the team and our performances have been okay but we have got to take the pain and disappointment that we've experienced in this game as motivation to fuel the fire for the game on Sunday.

"Otherwise if we keep putting it to one side and keep hoping things will turn around it won't just happen that way."

Whilst Bayer Leverkusen is a cut above in terms of opposition there was a feeling prior to the contest that anything Celtic could glean from this match would be perceived as a bonus.

Ange though is shifting the focus back on the players by sending out a stark warning that there will be no excuses for not winning matches and that the fans nor he will put up with it moving forward.

It was a point that he re-iterated to BT Sport and he laid it on the line to his men that he fully expects a reaction against Aberdeen on Sunday.

Ange said: "It's one thing being disappointed but there has got to be a reaction.

"We've got to keep persevering, we've been disrupted and we have had a number of injuries and we have rebuilt the squad and it is not surprising it is taking time.

"I still feel even within that we can be better. We just have to push through it and turn things around."

The Aussie is well aware that trotting out the same excuses about disruptions and injuries is getting tiresome and that patience with the recent run of form is undoubtedly wearing thin. It may be a sticky spell but Celtic just have to find a way of playing through it and rediscovering a winning formula.

Speaking to the newspapers, Ange admits that his side can ill-afford to pass up glaring opportunities in any match let alone against a top-class Bundesliga side.

It was also a recurring theme of mistakes defensively and offensively that did for his team and will continue to do if they are not rectified sooner rather than later.

Ange said: “It’s not just the mistakes.

“There were times when, particularly at the end, the players needed to be more disciplined.

“It shouldn’t have been a 4-0 game, irrespective of Bayer being a good side but we fell away at the end through lack of discipline - and for me that’s unacceptable.

“Look, it’s part of the experience. If you want to be a top player you have got to understand you can’t make mistakes like that. It is not just the mistake, it is your response to the mistake.

“They are a good side and they are going to punish you if you make an error. We had our own chances and that is just as crucial.

"If you go 1-0 up instead of 1-0 down then it becomes a different game. In both boxes, we need to improve. It is not about putting your arm around anyone, they have just got to realise it themselves."

Ange is pleading for his players' game-management in certain situations to improve and that individuals have to step up to the plate and take responsibility. Simply put, October is stocked full of must-win games.

You get the feeling it could be a long season for Ange, Celtic and their supporters.