RONNY Deila has never come across as anything other than calm and collected at Celtic.

A new side to him showed itself yesterday. At no point in what might have been a routine, ten-a-penny press conference, to preview tonight's Europa League game against Dinamo Zagreb at Parkhead, did he raise his voice or lose his temper.

There was previously unseen emotion, though, and plenty of it. Deila thumped his hand down on the desk. His gaze grew ever sterner and his face more animated as he built up a head of steam about what he is trying to do at Celtic.

He is a 39-year-old Norwegian manager out of his comfort zone and adapting as quickly as he can. As he opened up on the subject of Scottish football's attitude towards fitness and diet, which he clearly believes to be incompatible with competing in the Champions League, Deila conceded that he would live or die by the implementation of his principles. When he was asked if it was hard for a young, foreign manager to come to Scotland and impose fundamental regime change - Paul Le Guen's name was mentioned as a precedent - he agreed that it was, but that he saw no alternative.

"It is important to do the changes you want. If I want to get to the Champions League you have to look at the Champions League, look at the European level. And if you see the fitness in the Champions League it is unbelievable. Unbelievable! Celtic is a big club, we want to go out there. If we want to do that then we have to look outside the country [for the standards of fitness we need], not inside.

"There are many roads to Rome but I have to believe in my way. When you come to a new club, of course it takes time. You can ask Louis van Gaal about that. He has hard discipline and knows what he wants. It's not easy for a Norwegian to say. If Van Gaal was coming in and saying all these things you would be sitting there nodding your heads. But I come from Norway and they are only good at skiing!

"But I think Scottish football has gone [he gestured downwards with his hand]. The national team in the 1990s was good. There were Scottish players playing in foreign leagues. Now it's not the same. But football is going up and up. And what you did in the '90s is not happening now. If you went for a trip to Manchester City or Chelsea and saw the professionalism on display there I think you would be shocked.

"I really think the Scottish players are open to new things. Most of the things are not so new, they knew about them already. But are we talking Scotland or are we talking Europe? To win in Scotland we can still do the same things as before. But to succeed in Europe, you have to adapt to Europe. If you tell me that a player can be three or four kilos too heavy and play against Ronaldo, then good luck.

"I get irritated discussing it. You have to understand that the fitness is unbelievable out there. If you see Gareth Bale: that's Champions League level. So are we not going to try and adapt to that? Do you think Andy Murray eats chips? If Celtic or Scotland are not ready for that, then I will go back to Norway. It's no problem. I'm here to do something, I want to make something here. If you don't do it, then okay, I tried. But I really believe the players are enjoying it and want to adapt to it."

Le Guen was 42, just a little older than Deila, when he came to Rangers as one of European management's hottest tickets in 2006. The Frenchman was driven and idealistic, too. Deila would have approved of his views on "refuelling" not to mention his ban on Monster Munch crisps. But Le Guen could not get enough of the Ibrox players to buy into him and a personality clash with his captain, Barry Ferguson, proved ruinous. Le Guen was gone in six months.

There had been no significant resistance to him from any players at Parkhead, said Deila, only some healthy questioning which he welcomed. "I hope the players question things. We have arguments about a lot of things. But it's about understanding and talking. People have choices. But Celtic is going one way and that is upwards. If you are going to be into it, you have to make changes yourself. I have to adapt. I have to be a better manager than I was in Norway. I have to learn new things, sacrifice things that I would have done in Norway.

"It's the same for my players. They are playing for Celtic, the best club in Scotland, and we are going to compete in the Champions League. You have to make sacrifices for that.

"Dermot and Peter [Desmond and Lawwell, Celtic's major shareholder and chief executive respectively] are very intelligent. They wanted a change and that's why I came in. If not, they would have gone for a manager with much more experience and would have done it more like it was done before. It's a club thing."

It was quite a sermon from Deila, an intense, 23-minute window into the manager's mind. He was asked if he had been waiting to unload all of this for a while. "If I feel I'm not being treated fair then I get emotional. I am an emotional guy. So far things have been very good but this is something I think is very important. You don't come in and think you are the king. You have to work at how you want things and people have to get a chance. That's what I've been doing.

"I know what I want and I'm going to go for it. In the end only time will tell if I succeed or not. I am going to win things. That's why I am here."