RONNY DEILA considers it job done as he brings his squad back from their mid-season training camp in Gran Canaria.

The freezing conditions enveloping Lennoxtown will be something of a shock to the system of his players.

But they fully appreciate the heat is on as they begin to try and claw back the four-point title-race lead Aberdeen have built in their absence.

The time spent between games in Maspalomas - the Hoops lost 3-2 to Sparta Prague to add to their weekend defeat to PSV Eindhoven - was used to reinforce that the threat to four-in-a-row is real.

However, it was also emphasised ad nauseum that the destination of the Premiership crown remains very much in the hands of the holders.

So the players have been instructed to ignore what Aberdeen or any of the other would-challengers have done or are doing, and retain 100 per cent focus on what Celtic need to do. That is win games from here to the end of the season, beginning at Hamilton on Saturday.

The realisation this is not a one-horse race is slowly dawning on some of the players who have known only title success since they arrived at Parkhead.

But other, more-experienced team-mates, need no reminding what it feels like to fall below expectation.

Charlie Mulgrew is one such player. In his first spell at the club, he was a youngster trying to help the Hoops beat Rangers to the championship.

When he returned to Celtic, as Neil Lennon's first signing in the summer of 2010, that particular contest was as keen as ever, and Mulgrew was helpless to prevent the Ibrox side pip them to the title.

Subsequent events have seen the fortunes of both clubs dramatically divide, Rangers going into liquidation, Celtic into domination.

But ironically, it is Aberdeen, the club Mulgrew left on a free transfer to return to Paradise, who are now throwing down the biggest challenge to Ronny Deila's transitioning side.

And the midfielder/defender is in no doubt the time for Celtic to prove they have the mettle required to hold off all-comers is now.

Mulgrew said of the high-flying Dons: "They are looking a good side. They are looking a settled side. They are looking strong and they are keeping clean sheets.

"There is a lot of talk about them. But, at the end of the day, we just need to worry about ourselves. We have a couple of games in hand and it is about what we do. We feel that is the way it will be.

"We just need to put a run of results together, as we always have to do. More importantly now, we have to go on a good run of winning matches, get on top of that league and stay there."

Mulgrew has been on the other side of the scenario, doing all he could to help Aberdeen defy their underdog tag. He knows how tough it is to sustain such a challenge, and that the real test arrives when results are not going your way.

But the 28-year-old also recognises how important momentum can be, and that this currently lies with a Dons side which has won eight-in-a-row without even conceding a goal.

A knee problem has forced Mulgrew to sit and suffer as the Hoops have seen their own winning streak halted by a defeat to Dundee United and a draw with Ross County.

They got back on track with a win at Kilmarnock before heading to Gran Canaria, but the Scotland star was still in the stands that night and remains out of action.

Jason Denayer and Beram Kayal have been among the team-mates keeping him company in the treatment room, but both players got back playing in yesterday's defeat to Sparta Prague.

The Hoops side, which showed seven changes from the one which started against PSV, had taken the lead after just 24 seconds through Leigh Griffiths, but the Czech champions hit back with three goals before half-time.

Deila sent on Efe Ambrose and Nir Bitton to help the young side steady the ship, and another sub, Joe Thomson, reduced the deficit in the closing stages.

Bitton has assumed the anchor role vacated by Mulgrew, and appears to be growing in importance with every game. Mulgrew has been impressed by the rejuvenated Israeli international, who has enjoyed a new lease of life since having a heart-to-heart with Deila towards the end of last year.

"Nir has done well since he came into the side," said Mulgrew. "He is made perfectly for the holding midfield role. He keeps the ball well and sees a pass.

"Sometimes, when you come to Scottish football, things can be a bit quick. The tempo is a lot higher, but he has adjusted well to that now and is playing some good football."

Bitton, and others like him who, thus far this season, have been bit-part players, need to step up to the plate for the second half of the campaign if Celtic are to have any chance of grabbing the Treble Deila continues to believe is within their reach.

How big a boost in this quest the mid-season break will prove to be, only time will tell.

Much more important could be what Celtic do in the transfer market. The manager wants to clear out some of the deadwood, and hopes there are green shoots ready to burst through from the Development Squad.

But the Maspalomas Cup showed a number of those budding stars will require a little longer in the greenhouse before they can be safely exposed to the elements.

And the sooner Deila can once again call upon the likes of Mulgrew, James Forrest, Mikael Lustig, Anthony Stokes and Adam Matthews - none of who were risked in Gran Canaria after their injuries - the better-armed to fend off Aberdeen he will be.