It was not just that Celtic were the stingiest team in the league last season, but rather they were as tight-fisted as any side that has graced the top flight for the last 96 years.

The Parkhead side's record of just 17 league goals against last term gave them the best record for any Scottish team since season 1919/19 when Rangers shipped just 16.

Martin O'Neill's Celtic team of 2001/02 let in 18 - a modern best that Ronny Deila's men have just bettered.

Jason Denayer and Virgil van Dijk have claimed the bulk of the credit for that, given the understanding which the two centre-backs struck up.

That 19-year-old Denayer has been rewarded for his endeavours this season with a full international call-up for Belgium - recognition that flies in the face of John Guidetti's claims - underlines the commanding manner in which he performed for the Parkhead side.

With Denayer back at Manchester City looking to force his way into the Premiership side and Van Dijk sounding out about a bigger challenge, it may be that Celtic need an entirely new defensive wall next season.

While that may sound like a daunting task to replace two of the mainstays of Ronny Deila's side, Tom Boyd - part of that Celtic defensive team of season 01-02 who were of some repute -believes that the manner in which the Norwegian has the team playing may lessen the blow should Celtic line up for the start of the season with only one or, perhaps, neither of them in attendance.

"It is always going to be the two centre-backs who take all the adulation for the defensive performance," said Boyd.

"I don't think you can have anything other than praise for the understanding they developed together.

"Both players have a fair bit of pace about them and I thought they dovetailed very well.

"But I would also say that they were helped enormously by the way the team played. Ronny has got the whole team trying to win possession back as soon as the ball is lost and once they get it they are very good at keeping it. They have entirely dominated so many of the domestic games, especially in the second half of the season.

"The style of football has denied the opposition many chances in front of goal and has seen Celtic play the game pretty high up the pitch.

"I think it is a way of playing that has pleased a lot of people. It is good to watch.

"That last game of the season was excellent when Celtic thumped Inverness Caledonian Thistle and, in the final months of the campaign, I think you could see how much it has all come together.

"But mistakes at the back were at a real minimum. We know that Jason has gone back down the road and Dedryck Boyata has come in to take his place.

"He is another lad who comes to us well-rated and you would like to think that he will get the chance to link up with Virgil now. If that is the case, he is another who will hopefully find that the manner of Celtic's play means that defensively the pressure is kept off the backline."

Craig Gordon, too, has been pivotal to that defensive record being set. In many respects Gordon has had very little to do domestically this season and reserved his finest moments for the Europa League campaign.

But he has contributed to a cohesive defensive unit, and one that Deila will be reliant upon for getting Celtic into the Uefa Champions League group stage this season.

And in addition to the manner in which Deila has set out his side to play an attacking brand of football, Boyd believes that the Norwegian's fitness mantra has also been pivotal to the manner in which the team have taken the game to their opponents.

"I do think you can see that they are a fitter team than they were," said Celtic's last Treble-winning captain.

"I think if you look through the squad there are a number of players who look as though they have slimmed down by a fair few pounds and, at this level, and when married to the ability that you have, it can make a difference.

"If you want to play a version of football that is all about pressing, keeping the ball and keeping the play high up the pitch, you need all your players to be able to give their all for the 90 minutes.

"In that respect, Celtic attackers should be given a lot of respect, too, because they also put in a shift, making sure they worked back and really denied opponents the chance to play.

"You can only do that if everyone is buying into the manager's football philosophy and I think you can see that the players are."

That wasn't necessarily always the case, however. Deila had to negotiate a torrid opening period to his reign, his task compounded by the fact he walked into Neil Lennon's considerable boots.

That Lennon had been so successfull, compounded the challenge for Deila, but Boyd believes the foundations put in place by the current Hoops boss can have a lasting effect.

"I know John Collins well and I know the way that both men want their players to be. As a player you must buy into that.

"You know that ultimately you need to give it everything, but it is not just players that can see the rewards.

"I think everyone around the club in those last few months really enjoyed the football they were watching. It was easy on the eye.

"Celtic are pressing, they are creating chances, they are looking to win and win well. It all augurs well for the future season."