FAMOUSLY, one could take the word of Fergus McCann - back on Saturday at the stadium his vision helped build - to the bank.

Ronny Deila is displaying the same aptitude for plain speaking followed by substance.

The Norwegian seeking to place his imprint on history will not fail through lack of effort. Deila is in danger of finishing the season with arms like Popeye such was his constant flailing at his team to push up, to press, to attack, attack, attack.

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He will judged mercilessly on the basis of achievement, with Champions League qualification a prerequisite to a season of unalloyed success. He has, though, shown that not only are Celtic improving but growing accustomed to a style which stretches their energy and intellect. Basically, Deila wants his players to outrun and outthink opponents.

This demand was answered emphatically on Saturday. NK Maribor are capable of presenting a more testing examination on Wednesday.

The most conspicuous element of Celtic's play was the demand from the bench to press and the desire on the field to carry out this mandate. The Celtic starting front six of Callum McGregor, Stefan Johansen, Charlie Mulgrew, Jo Inge Berget, Anthony Stokes and Kris Commons were irresistible: clever on the ball, desperate in their attempts to reclaim it and keen to make runs that would stretch the United defence. They were aided and abetted by a criminal defensive performance by United.

It was six. It could have been more. It would take Crimewatch not Sportscene to analyse adequately the failings of the visitors but, suffice to say, four of the six goals conceded were the result of set plays. Jackie McNamara was correct to lament this but Deila also had a point when he observed that his team had been working on converting more chances from set pieces. However, when Kris Commons scores from a corner with a header at the near post - jumping just high enough to allow a bus ticket to be inserted beneath his sponsored boots - then the tide of cause and effect is running strongly towards culpability rather than creativity.

The second most pertinent factor emanating from a thrilling match was Celtic's sloppiness in defence. Jason Denayer, on loan from Manchester City, had three early touches, two of which should have ended in United goals. The other nestled behind Radoslaw Cierzniak to be the first of the half-dozen. He could be forgiven early sloppiness, particularly as he later showed both technical ability and excellent pace, given his inexperience. Craig Gordon had to make some decent saves and United scorned a series of chances before John Rankin scored with a deflected shot.

Celtic, then, were formidable in attack but fallible in defence. Deila is certainly idealistic, but he is realistic too. He knows this untidiness at the back must be addressed if NK Maribor are to be overcome.

The manager, too, was sharp both at half-time and full time. At the interval he withdrew the impressive Johnasen, keeping the industrious and skilful midfielder fresh for midweek. At full-time, he kept his other players grounded by declaring he wanted more. Deila has a habit of referring to moments in the match as "sleepy". There may have been the slightest of lulls between his side's fifth and sixth goals but this was a game as becalmed as the local pool during the school holidays when the wave machine has been turned on.

It is obvious that Deila wants his side to sustain the pressing game in defence and the speedy attacking style for 90 minutes. This was too much for feckless United but Deila is aware that other sides will be more resilient. Domestically, Celtic can book Mr McCann for a repeat performance of flag unfurling now if they wish. Europe, whatever competition the club play in, is a different matter.

Deila has to assess the fitness of James Forrest, who strained a hamstring after coming on as a substitute, and Adam Matthews, who pulled out of the first team at the last moment with a calf injury.

He may also have to rethink his strategy. Deila was so cavalier against Legia Warsaw in the first leg that he could have been riding a horse while wearing a hat with a feather in it. He must formulate a plan that addresses the necessity of being defensively strong in Slovenia.

The man whose acumen created the modern Celtic Park had a ceremonial role on Saturday but his presence was a reminder that success is built on strong foundations. The defensive wall must hold against NK Maribor.