CELTIC manager Postecoglou last night admitted that losing 4-0 to Bayer Leverkusen at Parkhead was “unacceptable” – then revealed he will not be abandoning his attacking game plan in the wake of the heavy Europa League defeat.

The Glasgow giants were hammered by their German rivals at home after conceding goals to Florian Wirtz and Piero Hincapie in the first-half and Lucas Alario and Amine Adil in the second.

They are now in bottom spot in Group G after two matches and face an uphill task to finish in the top two in their section and progress to the last 32 of the competition.

However, Greek-Australian coach Postecoglou, whose side have now won just two of their last eight games, believes his men will learn lessons from the heavy reverse and improve in future as a result. 

“If you accept it, you won’t grow from it,” he said. “You need to take away the disappointment. If we’d lost 2-0 or 2-1 tonight, okay. But when you lose 4-0, it’s not enough. It’s disappointing and that scoreline shouldn’t have reflected that game. I can’t 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. I want to be a team that goes at it and takes the game to opponents.

“That’s the kind of team we’re going to be and that’s what I’m trying to build. The process, yes, it takes time and we are going to cop some knocks on the chin like we did tonight, but that doesn’t mean you have to accept that. You need to understand that’s avoidable if you do certain things.”

Celtic created numerous scoring opportunities and were repeatedly denied by Leverkusen’s brilliant Finnish goalkeeper Lukas Hradecky.

Asked if he still had faith in the attacking style of play in the wake the defeat, Postecoglou said: “Yeah, I don’t see any reason why not to. They’re a quality team and there’s always a possibility you’ll get punished. But I think we created enough our own opportunities to cause damage and we didn’t take them.”

Postecoglou was disappointed with the errors that Celtic made at the Leverkusen goals and confessed that they must do better defensively in Europe.

“Look, it’s part of the experience,” he said. “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 errors and they are going to create chances as they did tonight. But 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.”