A SIMMERING disagreement between Ronny Deila and his predecessor as Celtic manager, Neil Lennon, continued yesterday as the subject of the fitness of the club's players was raised again.

Lennon has previously said it was disrespectful of Deila to publicly question the condition of the players he inherited over the summer but the Norwegian gave a firm response on the eve of tonight's Europa League tie against Dinamo Zagreb. Deila said all managers had different ways of approaching the job and it was not his fault if Lennon had been irritated by his comments.

Deila conducted his press conference with previously withheld passion yesterday as he insisted he would "go back to Norway" if Celtic and Scottish football were not prepared to accept his ideas and his methodology.

"Maybe I see things differently," said Deila, who has changed the players' diet and banned fizzy drinks since he took over. "For me, to be professional is to be a 24-hour athlete. If not, then you can go and start working outside football. That's not so hard. You can be amateurs again.

"You have to understand that I can't be stupid when I say things like that and if Neil gets irritated by me saying we can work on how we eat and improve that's up to him.

"For me, I think, from what I have seen abroad and what I have experienced myself, it is important. We have different ways to do it."

Deila's view was that he had never criticised Lennon's way of working, but that when he took over as manager in June he inherited players who were carrying injuries, and brought others into the squad who were not as fit as he wanted.

"When I see the tests they are doing I see they have a lot to improve," he said. "It's not about what they were doing before. It's all about how they are in the moment now.

"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's 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, not inside. That's because the levels [we need to reach] are not inside the country they are outside."

In terms of tonight's second fixture in Group D, after the creditable opening 2-2 draw away to Red Bull Salzburg, Deila said Leigh Griffiths was likely to be involved and was even a contender to start the game, despite apparently having fallen out of the picture in recent weeks and been linked with a possible loan move to Hibernian. John Guidetti is ineligible for the game and Stefan Scepovic has a slight knock, although Kris Commons is available after a thigh problem at the weekend.

"Leigh can be part of the game. He's in the squad, so we'll see," Deila said. "I talk with my players about what they have to improve on or not. He knows exactly what those things are and he really wants to improve as well. First of all, he has to get up his fitness. That is his first task. That's something he is also aware of.

"He's a good football player and he scores goals. But I know he can be much sharper and stay on top of his game for 90 minutes. Once he has that then he will be so much better.

"He is going to stay here, so there's nothing more to talk about. He's told me he wants to stay. We need him and we have a lot of games. So that's how it's going to be.

"Dinamo Zagreb's level is quite similar to Salzburg. They are a good team and we have to be at our best. If you don't believe then you have no chance. We believe we can beat Zagreb. In the training we focus on it. There has been a good attitude."

Captain Scott Brown said that Celtic had a responsibility to fly the flag for Scottish football as its sole surviving representative in the European tournaments this season. "Everyone is trying to put Scottish football down so we have to be the backbone of Scotland and try and keep things going," said Brown.