CHRIS Sutton believes the Celtic board must back Ronny Deila - now they have decided not to sack him.

The former Parkhead favourite, now employed as a Scottish football expert for BT Sport, believes the club's supporters have been accustomed to "bang average dross" at times under the Norwegian.

And the only way to lift the malaise among the supporters is by spending big in the January transfer window to safeguard the charge for a Treble.

“I think there’s an air among the supporters of being resigned at the minute to bang average dross at times," said the Englishman, ahead of tonight's live match against Dundee United at Tannadice.

"If they were going to relieve Ronny of his duties this was the time to do it. 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 unfairly to make an instant impact in the biggest games of the season.

"But if Peter Lawwell makes the decision to keep him there is no point in not backing him, because he is hanging him out to dry even further," he added.

"If you keep him get behind him and give him the tools he needs."

Celtic have been quiet so far during the window, with Ryan Christie finally joining the club after his loan spell at Inverness Caledonian Thistle. But the arrivals of the likes of Steven Fletcher, Icelandic striker Kolbeinn Sigthorsson, Norwegian midfielder Kristoffer Ajer, and Serbian defender Aleksandar Pantic could help boost morale at Parkhead and help the club build towards next season's Champions League qualifiers.

Ironically, Sutton also feels the club could profit from using the route currently being exploited by Rangers, of taking promising players from England's lower divisions.

“I think you do need to push the boat out now and again," said Sutton. "There comes a time when Celtic have to try and sign players who are better than what they’ve got.

"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? It’s January 14 now and I don’t understand why they’re hanging about.

"It doesn't matter where they come from," he added. "I have to say I like the boy Crooks who has signed [for Rangers] from Accrington.

"I know he was highly regarded by various clubs. That might be a logical way for Celtic to go."

While Sutton can hardly fail to be impressed by the goalscoring form of Leigh Griffiths - he is one goal away from his half century of strikes for the club, and will have made it to that tally in fewer starts than any previous player in history - he feels that Deila's Celtic are too reliant on one-man for their goals.

No other Celtic player has hit double figures this season and Sutton feels the number of attacking midfielders which the club possesses proves that the 4-4-2 shape used against Stranraer last week is unlikely to be more than a short-lived experiment.

“He [Deila] certainly needs to address the situation because if Griffiths gets injured, and hopefully that doesn’t happen, then it’s a big concern," said Sutton. "At that point you’re going to need another reliable striker.”

‘Watch Dundee United v Celtic in the Ladbrokes Premiership live and exclusive on BT Sport 1 from 7:15pm on Friday 15 January. Visit btsport.com’