WELL, that'll be that, then ...

the strength of the challenge to Celtic making it four-in-a-row has been fully exposed.

The 4-0 destruction of the not-so-dandy-Dons has fired the Hoops six points clear, with the opportunity to make it nine when they play St Johnstone on Wednesday.

It's surely no coincidence Celtic finally started to put together this decisive run of eight straight league wins - conceding only one goal in the process - during the hiatus between the Europa League Group Stage and their appearance in the last 32.

Now, with Europe over for the season, all their concentration and resources are being channelled into what their fans call the Treble, and Ronny Deila refers to as the Triple.

They can collect the first of these trophies in a fortnight when they meet an alarmingly-ailing Dundee United at Hampden in the League Cup final.

Before then, the same Tannadice club - the last team to beat Celtic in domestic competition, back on December 21 - will try to derail the Hoops' Scottish Cup-winning aspirations when they meet in next weekend's quarter-final.

Celtic can go into these cup ties with a confidence-boosting cushion in the league.

They moved a huge step towards retaining their crown with their summary dismissal of an Aberdeen side which carried not only the hopes of their fans, but of the football nation outwith Paradise, longing to see a genuine contest right down to the wire.

Sure, the final scoreline from yesterday's high-noon showdown did not truly reflect the events of the 90 minutes.

Indeed, Deila concedes it would have seemed unthinkable as he watched the visitors pull his side this way and that in the opening 37 minutes.

"Of course, I was worried as I watched the way we started," he conceded. "It was because we didn't get our legs going as quickly as we normally do.

"I can understand why, when you consider the fixture programme we are in. But the important thing was we were calm and we dealt with difficult situations, like set-plays.

"We defended well in the box, and we also scored with a set-play, which is something I have spoken a lot to the players about. That changed the game.

"And, by the last part of the first half, and in the second half, there was only one team on the pitch."

Indeed, even his counterpart, Derek McInnes, would have to agree that, by the time the game ended, his Dons side was unrecognisable from the one which took the game to the champions.

The winning margin could easily have been double, such was the profligacy - if not mercy - shown by the regrouped Celtic team in a second half when they cut through Aberdeen with ease and aplomb.

It ended so one-sided that even the feistiness which typifies such encounters gave way to a show of pity, Efe Ambrose - filling in at left-back for the injured Emilio Izaguirre - apologising to Steven McLean after nutmegging him on the halfway line.

It must have felt like insult being rubbed into injury, given that Celtic were so far on top by then.

A first-half goal from Jason Denayer - when Aberdeen failed to deal with a corner - left the visitors feeling hard done by so well had they played to that point.

They came out looking for an equaliser, but, like in the first period, failed to make it count when they were on top.

That left the door open for Leigh Griffiths to make it 2-0 from the spot after Mark Reynolds committed a needless foul on Stefan Johansen as the midfielder moved away from goal.

Gary Mackay-Steven was allowed to run straight down the middle of the pitch with the Dons' defence in disarray and retreating before he scored No.3 off Scott Brown's left-hand post.

And it was 4-0 with 10 minutes remaining, Johansen maintaining his prolific strike rate when he scuffed home a shot after Adam Matthews had made a penetrating run down the right wing.

McInnes' resorted to removing main striker, Adam Rooney, and replacing him with centre-back, Ash Taylor, in a damage-limitation exercise for the closing minutes.

Unfortunately, by the time their back door was bolted, Celtic had run for home, the points safely in their saddle bag.

They have now shown Aberdeen a clean set of hooves, having defeated them on all three occasions their paths have crossed this term, with an aggregate scoreline of 8-2.

Without the two victories in their previous head-to-heads - at Parkhead in September during Tonev-gate, and when 10 men hit late and hard at Pittodrie in November - the Hoops would not have gone into yesterday's third meeting in front in the title race.

Now, as Spring has sprung, the lead is once again six points, with Wednesday's game against St Johnstone in hand.

Deila made no attempt to hide his delight and pride in his players. Why should he? They faced up to all Aberdeen could throw at them, then came back with more than their challengers could handle.

Deila reflected: "We struggled in the beginning because they are a good team. They were fresh, and we didn't get up to the tempo we have done lately.

"But we came more and more into it during the half and, in the second half, we were brilliant. We were disciplined, organised, balanced and moved the ball quicker.

"They couldn't cope with the runs we had behind them. I'm so happy for the performance and the result, and I'm proud of the boys."

Deila added: "It's so hard to play so many games. We didn't arrive in Glasgow until 3 o'clock on Friday morning (after their game in the San Siro). That's a tough one when you are going to play two days later."

Now, such handicaps are behind them, and the route to the Triple/Treble is much less obstacle-strewn.