CONNECT four is the game Celtic have now mastered.

And it is been reflected in the seven clean sheets they have now racked up, the best defensive run in Ronny Deila's time in charge of the Hoops.

Ironically, new signing Stuart Armstrong is the last man to have found the Celtic net, when he scored the winner for Dundee United on December 21.

The Hoops want to extend this thou-shall-not-pass run by another 90 minutes when they face Partick Thistle tomorrow night.

In the Glasgow derby postponed because of a flooded Firhill pitch on January 1, their aim is to re-open the gap between themselves and Aberdeen at the top of the SPFL.

Having a settled back four has been the catalyst for keeping the back door locked.

The return of Jason Denayer to partner Virgil van Dijk, and Mikael Lustig at right-back to add balance to the rampaging runs of Emilio Izaguirre on the left flank, has provided the solidity which had been missing, resulting in the individual and collective errors being erased from their game.

But, along with this back four, the middle four of Van Dijk and Denayer playing behind Scott Brown and Nir Bitton, has also been a key element in ensuring Craig Gordon is seldom called upon.

When he is, the experienced keeper is more than ready to fly into action, as he proved again at Dens Park on Saturday when his watching brief was interrupted by a deflected shot from Paul McGowan which forced him to extend his right arm like Stretch Armstrong to keep his side ahead in the Scottish Cup tie.

But Deila does not allow all the credit for this lack of scoring opportunities afforded to the opposition to be placed at the door of the keeper, the back four or even the sitting midfielders.

The manager insisted: "Everything starts with good defence, and we are defending very well.

"We are winning balls in good situations, then we can counter-attack or keep the ball.

"That's a very important thing, and we we defend now like a team.

"It starts at the very front, with Leigh Griffiths."

Evidence in extremis of that was provided when the striker - already flying high from scoring the opening goal from a Lustig cross - lost possession to James McAlister 35 yards from Dundee's goal.

As the Dundee midfielder raced past Van Dijk and Denayer on halfway and thought he had a clear run at Gordon, it was Griffiths who chased back to rob him of the ball and avert any danger.

That's not exactly what Deila wants to see Griffiths forced to do, but it does illustrate the manager's point.

"The wingers are also working hard when the opposition has the ball, and Kris Commons also worked hard before he had to go off after he felt the back of his thigh," said the manager who now claims the Hoops "Look more like a Ronny Deila team".

The addition of Stuart Armstrong and Gary Mackay-Steven - both ineligible for domestic cup ties - means there is no need to take any risk with Commons tomorrow night against Partick Thistle.

The squad now has more depth and quality than at any time since Deila took over, and genuine competition for places is present in every position, except left-back where the Duracell bunny that is Izaguirre shows no signs of needing back up.

Along with the addition of Armstrong and Mackay-Steven, the carefully-programmed return of James Forrest gives Deila confidence that, ahead of so many important and taxing games this month which will determine how many trophies he can collect in his first season, he has the weaponry to shoot for the moon.

"James has been out for a long time, in terms of games, and it was a good performance from him at Dundee," said the Norwegian, who remains confident the explosive-but-injury-plagued-winger can play a big part this term and give his team-mates an extra boost because of the out ball he offers them when they are under pressure.

Deila added: "It is about team spirit, and it is about 11 players defending so that it is very hard to break us down."

As recent weeks have shown, it is also about 10 players attacking, with Lustig, Izaguirre and Adam Matthews all getting in on the scoring act.

At the weekend, Lustig delivered the crosses which led to both goals, scored by Griffiths and Stefan Johansen.

Unfortunately, the Swede later picked up an ankle knock and looks like joining Commons on the absentee list tomorrow night.

But while Lustig's importance to the side is not underestimated or down played by Deila, he is comforted by the fact that, in Welsh international Matthews, there is a more than able deputy.

That's just as well, given how much of the season Lustig has already missed, the hip problems which have already seen him go under the knife still restricting how hard he can train and how long he can last in matches.

He has also been troubled by a recurring hamstring injury, perhaps not unconnected to the underlying hip damage.

Deila is philosophical when considering the issues surrounding his fellow Scandinavian and said: "This is just an unfortunate knock, and you can't do anything about that.

"The injuries with the muscle problems, stretched and pulled muscles, we have to try to get them away.

"But he looks good now and is training well, as is Adam Matthews, as well.

"Adam has been training and playing for a long time since his injury, and I have no worries that he is going to play instead." .