CHRIS Sutton never shirked a tackle as a player and he doesn't mince his words as a pundit either. The former Celtic striker, now employed as a Scottish football expert for BT Sport, senses a malaise about his old club as 2016 begins. The club have chosen to back, rather than sack, manager Ronny Deila but the Englishman feels it is now or never if the Parkhead side are to show the improvement required to return to the Champions League next summer.

“I think there’s an air among the supporters of being resigned at the minute to bang average dross at times," said Sutton. "In terms of progression, have they progressed in Europe since last season? No. Have they played the style of football Ronny promised? No. Peter [Lawwell] has kept him in a job and that makes this five months till the end of the season absolutely critical. It’s ‘now or never’ really."

Celtic circa 2016 are in the unique position where they could end up with a treble - only the fourth in the club's history - and still not entirely convince everyone that they are the real deal. Apportioning blame for all this is a complicated process. While Sutton feels Deila has stayed too wedded to his preferred 4-2-3-1 shape (he feels last weekend's 4-4-2 shape against Stranraer will only be a short-lived experiment) and consequently the side are too reliant on 24-goal striker Leigh Griffiths, he doesn't feel the Norwegian has been helped by the club's recruitment policy, while players such as Stuart Armstrong and Gary Mackay-Steven who came in and looked the part this time last year have to take their own share of personal responsibility for their failure to kick on. Having decided against sacking their manager, Sutton feels the least the club can do now is back him, although the suspicion persists that Deila is one horrific result away from the PR disaster which could stop his time at Celtic in its tracks.

"If they were going to relieve Ronny of his duties this was the time to do it," said Sutton. "It would make more sense to get someone in now and let them get the feet under the table so it’s not the scattergun approach in the summer where you get someone in you are asking him unfairly to make an instant impact in the biggest games of the season. If Peter Lawwell is backing him – which he seems to be – then surely there comes a time when they have to speculate a bit and get an experienced player in. So why wait? I don’t understand why they’re hanging about.

“I look at Celtic this season, and which players have played better from last season?" he added "There aren’t that many. [Kieran] Tierney’s come to the fore, he wasn’t playing last season. [Tom] Rogic’s done a bit better, you’d also of course say [Leigh] Griffiths. But after that, I think you’d be struggling.

“I think there is an over reliance on one source of goals," he added. "I’m sure Ronny’s trying to address that, but then so is every club in Britain. In the end it doesn’t matter what system you play, as long as you are creative and winning. But I don’t think Ronny will go with 4-4-2 long term because look at the amount of so-called No 10s they’ve got at the club, it’s ridiculous."

Sutton uses the example of Martin O'Neill during an Old Firm match at Ibrox to demonstrate that all the best managers must be prepared to alter some tactical ideas when the occasion demands. The versatile Englishman was in the toilet at Ibrox and missed the instruction that he was changing to a 4-4-2 and was suddenly required to play at centre back rather than central midfield. "I realised eventually," he recalls, "purely from the amount of abuse I got."

After some notable successes in buying in rough diamonds, sharpening them up and selling them on, the success rate of Celtic's recruitment arm under John Park has started to slow up. While the Englishman feels the time is right to push the boat out on a marquee name such as Steven Fletcher, he also feels the club may have success in following Rangers' lead by snapping up promising youngish players down the English league system.

"We can all look at the manager but there does come a time when the responsibility falls on Peter Lawwell," he added. "The strange thing is that they could actually win a treble and, historically, you know how difficult that is.

“You do need to push the boat out now and again. There comes a time when Celtic have to try and sign players who are better than what they’ve got.

"It doesn't matter where they come from. I have to say I like the boy [Matt] Crooks who has signed at Rangers from Accrington. I know he was highly regarded by various clubs. That might be a logical way to go. But there seems to be issues in terms of who is signing the players. Something doesn’t add up for me because if you go back Celtic are not finding the players they did."

Things might not be progressing entirely to plan at Celtic but they could be worse. Friday's opponents Dundee United have won just two league matches all season, and Sutton believes chairman Stephen Thompson should concentrate on accepting his share of the blame, rather than pinning it on the recruitment of former boss Jackie McNamara. "The wheels started to come off there when he [Thompson] hung Jackie out to dry over the contracts," said Sutton. "It snowballed. Why he stayed on, Jackie needed his head read at that time because it was only going to go one way."

Watch Dundee United v Celtic in the Ladbrokes Premiership live and exclusive on BT Sport 1 from 7.15pm tonight. Visit btsport.com