Football games frequently change during the course of their 90 minutes.
It was certainly the case here as Celtic dominated the first phase and gave Dundee United a masterclass in completing eye-catching manoeuvres in clinical and thrilling fashion.
What happened to them in part two of this compelling game, however, is another story, one effectively told by the changes the home side made, both in personnel and in attitude, but without the all-important end product.
Georgios Samaras and Anthony Stokes were the Celtic finishers, the kind you need, if only to reward colleagues on top of their form and generous with their creativity.
The Greek striker's fifth-minute goal set the tone of the remaining 40 minutes of the opening phase and when Stokes hit a second 20 minutes later, there were expectations of a deluge of strikes from the visitors.
Celtic manager Neil Lennon, did not rein in his compliments for his team, declaring them "magnificent", though often "overlooked". He said: "A lot has been said about Dundee United and their young players, and rightly so. Aberdeen have had a lot of praise as well. I think sometimes we are taken for granted.
"You saw what a good team we are. Some of the football was sublime, exhibition stuff at times. Sometimes our performances are overlooked. People say there's no competition, but you still have to go out and do it and I think it gets taken for granted sometimes."
Lennon praised the performance of Efe Ambrose, supreme at centre-back alongside Virgil Van Dijk, but insisted he was unconvinced the Nigerian, transferred from the Israeli club, Ashdod, was a natural in that position.
"He's been a great signing," he said. "We got him for £800,000 and his performances in Europe last season were fantastic. I'm not convinced he's a bona fide centre-half but he's grown into the role. He had an excellent partnership last season with Kelvin [Wilson] and he's formed a fantastic partnership this season with Virgil."
If United's players looked weary and bedraggled going in for their half-time cuppa, it was difficult to imagine what Jackie McNamara, their manager, would be able to say to them in the face of the difficulties they had faced in the opening 45 minutes when, aside from two long-distance thunderbolt shots from Nadir Ciftci - both straight into the arms of Fraser Forster - they failed to make any impression.
Celtic's fluency of movement and quick-fire passing were impressive, not to say deadly. In shaking off his marker as Kris Commons sent a free-kick into the United area, Samaras gave himself sufficient space and time to volley the ball home from 12 yards after just five minutes and dent whatever early confidence the home side may have had.
It was the signal for a series of attractive, attacking moves from the champions with Samaras at the heart of most of their play and Beram Kayal, in his first start since October, acquitting himself well in midfield.
When Stokes burst into United's penalty area after 25 minutes and sent his shot high into the net, however, it was game over, though with Gary Mackay-Steven replacing Brian Graham for United after the interval, there was a greater urgency in their ranks and, at least for meaningful spells, they threatened the Celtic defence. Suddenly, Ambrose and Van Dijk had to work harder for their wages.
Celtic came close to increasing their lead on the hour mark as Sean Dillon's loose ball in defence was pounced on by Leigh Griffiths, introduced for Liam Henderson early in the second half. But, while the striker's shot was good, Radoslaw Cierzniak made an acrobatic save, quickly followed by a block of a Commons effort.
Celtic goalkeeper Fraser Forster had to make two spectacular saves - from Mackay-Steven and Stuart Armstrong - late on, but there was no way back for United.
As he looked ahead to next weekend's William Hill Scottish Cup semi-final against Rangers, McNamara said: "We'll need to have the same energy we had in the second half but from the start of the game and not give away silly goals from set-pieces."