THE old authoritarian mode of management has long left the dressing room but the sense of fear has not. This summer, as the Celtic players headed off for respite before a punishing schedule of Champions League qualifiers, the temptation to succumb to the holiday treats would have been eyed with some trepidation.

“If they come in and they are two-and-a-half kilos over what their best weight is then they won’t train with the squad," said Brendan Rodgers. "It’s very simple, they can train but it won’t be with the first team."

The difference between the squad he oversees now and the one which he inherited two years ago from Norwegian manager Ronny Deila was highlighted starkly by Rodgers.

“Where the culture is now, our worst player this season in terms of the tests and measures we do, was our best measure when I came in,” he revealed.

The fitness results haven’t been the only difference of note. Rodgers’ first European qualification game with Celtic resulted in an ignominious defeat to Gibralter Red Imps but last week the first step of a quadruple hurdle was negotiated with ease. Celtic overcame Armenian side Alashkert with little fuss on Tuesday night to tee up what is essentially a formality of a second leg on Wednesday night but key to being able to approach those games with some confidence is having a strong physicality at the core of the side at such an embryonic time of the season.

“Old school was you came back to get fit,” said Rodgers. “The message we say to these guys is you’ve got to come back fit then we’ll add to it. There’s no hiding place. You’ll see it on the pitch. They come in and do a battery of tests and measures with the medical team and sports science team. We analyse every part of their performance from taking their drinks and compliance with medical work and everything else. We’re asking the players to be the best they can be every day, not just when they want to. So that’s looked at on a daily basis.

“Football is science and art, and for me it’s an art, but what you can’t deny is the science of the game is absolutely and it’s that fusion between both. And especially when you play a technical game, if you play a high-level technical game if you’re not fit the first thing that goes is your technique. So in order to play with intensity, to play with aggression and play all of that you need to be super fit, simple.

“Sometimes the bleep test can be more mental than physical but it gives you a good gauge, in terms of the mental and physical fitness of players. Of course, when they come back and you are measuring body fat and that side of it, that’s about lifestyle. There is no hiding from that.”

If the physicality of the Parkhead side has been evident in these early performances, Rodgers is confident that the mental aptitude to cope with the pressure of the qualification process will be clear as the games go on. The anticipation is that Rosenborg will overcome their surprise 1-0 defeat to Icelandic minnows Valur to tee up a second successive meeting with Celtic at the qualification stage and it is the confidence to negotiate some of the tensest games of the season where Rodgers believes his real mark on Celtic can be keenly sensed.

“If you can win away from home 3-0 in your first game then come home for your second one...you’re never totally guaranteed but it puts you in a good position,” he said. “As I’m talking I’m smiling because we won 5-0 against Astana and then for a 20-minute period it wasn’t so comfortable.

“But what’s pleasing for me year on year is within the squad you sense the calmness and the mentality and the approach to it. We had a block of 20 minutes last year but apart from that I thought it worked out quite well. This year is a bigger challenge for us because there are extra games.

“But I was really pleased with lots of things from the other night, in terms of the physicality of the team, playing against easily the best team we’ve played in the seasons I’ve been here in that first round. They were quick and dynamic and that can really catch you out early on in pre-season. But we dealt with it and showed our strength and fitness at the end.”

Given the lead Celtic have established there could be room for some of the fringe players to stake their claim. It remains to be seen what part there is this season for Ryan Christie and Scott Allan to play. The latter has been suggested as part of the deal to bring John McGinn to the club and while Rodgers talked up the qualities of both players he did accept that they made need to move on in order to get the full exposure to regular football that they wish.

“We played 61-games over the course of last season, so in the main there will be 50-plus games plus international games,” said Rodgers. “So it’ll only really be the case are both boys able to come in and be in a Celtic squad, for sure absolutely. Can I give them the game time that they want at this stage of their career? I think that’s the only question mark really and that’s a conversation that we’ll have.

“Then really it’ll be about the player and what they feel really. But both players have done very well. I’ve always liked Scott Allan, I’ve always seen him as a talent but he knew that after his experience at Rotherham, he needed to be playing and he did that and did very well at Hibs. So he is a player I like, he’s got speed, he’s got qualities, I think he’s got more to show.

“His career has drifted a wee but I like him a lot as a person and he trains very hard. I think those guys will look and think about what this group of players has done over the last couple of years. Ryan and Scott both have big talents. But it is, again, about OK, am I going to get enough game time? That’s going to be the ultimate decision that will have to be made.”