WHENEVER Ronnie Deila spoke about certain players not being fit enough at Celtic Park, everyone knew who he meant.

The person more aware than anyone else was Leigh Griffiths, for two reasons. Firstly, the player was him, and secondly, his manager would tell him straight to his face that he wasn't shaping up. The Norwegian just wouldn't name the guilty party in public.

Griffiths was already sailing close to the wind. His talent has never been in question but his attitude was forever being questioned, and Deila for the first few months of his time at Celtic Park did not know what to do with this particular player.

So they had a heart to heart in October, a few home truths were said and the penny dropped.

Griffiths was happy to admit all of this while promoting the international friendly against Qatar this week and then the vital European Championship qualifier against the Republic of Ireland a week on Saturday.

The fact Griffiths was being asked to represent Scotland at all was proof of how far he's come since picking up a couple of good habits, while at the same time dropping a few. Some were more easier than others to give up.

"The manager had his reasons why he left me out," said Griffiths. "I had to go and work on aspects of my game and get fitter. That's why I'm playing now. It's not just one thing. It's getting stronger, working harder in the gym and in training, changing my off-field stuff, changing my diet. I've done all that.

"My personal view is that he didn't think I had it in me to do it. I'm thankful I've changed his mind with everything I've done. It's not just my diet. In Norway, there's a big thing about body fat.

"My body fat probably wasn't up to his standards. I've never been the fattest of guys over the years. I've tried to work on keeping my body fat down and not eat as much as what I should've been eating. I'm trying to eat the right foods.

"I was a sucker for fizzy juice - I have a sweet tooth for Irn-Bru - but now it's all about diluting juice and water. The manager made a comment about my off-field antics and what happened over the last few years. I think he just wanted me to change that. He said he saw potential in me and if I cut all that stuff out I could be a real top player. I think, since the middle of January, I've started to show what I really can do."

And how is the body fat now?

"I am not answering that. It could still be better. The manager said that before I left. I did get the body fat count down in the second half of the season because I worked hard."

Griffiths is a good interviewee in that he is open, perhaps too open, and always answers questions in a forthright manner. For example, he was happy to admit that Deila clearly didn't think the 24-year-old was up to giving up the Irn-Bru and fatty dinners.

"The way he was looking I guessed he was thinking that he wanted me to change, but didn't think I had it in me," said Griffiths. "I went out of that room after a meeting with him determined to get my place back in that team.

"I spoke to Neil Lennon about it last season when something happened and he said that if I wanted to be a Celtic player then I would have to put all that stuff down. I was disappointed when he left but the manager came in and after pre-season I obviously wasn't fit enough to be in the squad. And since October I haven't missed out on a squad.

"You can't be chosen for Scotland if you are not playing for Celtic. I had no problem not being in the squad, but since the turn of the year I've hit a good run of form. I was disappointed to miss out on the last one, but I've got myself in now."

Griffiths went on to have a fine season after he and Deila's chat. He found his goalscoring touch but more than that, his all-round game improved immeasurably.

Chances are, Gordon Strachan will start him against Qatar and go with Steven Fletcher in Ireland. If the Celtic man does get his chance, he is in a much better place to do himself justice for his country, something he did not do when he led the line away to Croatia a couple of years ago.

"As a lone striker at Celtic you need to work on all parts of your game," he said. "It's not just about scoring goals, it's about link-up play and movement and stuff. The manager wouldn't have put me in against Inter Milan and teams like that if I wasn't ready.

"Gordon wanted to go with form in that (Croatia) game. I'd played as lone striker at Hibs. I wasn't as experienced as I am now so hopefully I get the nod on Friday. If so, I'd be ready to go."