ON a night when Celtic’s record books were scrutinised to confirm Kieran Tierney at 20 as the club’s youngest ever captain, a small step was taken towards a historic successive treble.

Despite the fact Brendan Rodgers put out, with one or two exceptions, a team of weans, there was always only going to be one winner at Celtic Park. The holders cruised through to the Betfred Cup quarter-final.

Kilmarnock do have ambitions to be a top six Premiership side and, yet, they were well beaten to the point it was quite embarrassing at times by Celtic’s third to fourth team.

Read more: Brendan Rodgers: Kieran Tierney was born to be Celtic captain

It was certainly one of the youngest Celtic starting elevens in many a year. Five teenagers, Kundai Benyu, Kristoffer Ajer, Anthony Ralston, Calvin Miller and Eboue Kouassi all began. The back four’s average age was under 20. It mattered little.

Lee McCulloch, the Kilmarnock manager, won’t lose too much sleep over this. The Ayrshire club won this competition in 2012, beating Celtic in the final, but things are different now and survival is about all that matters to them this season.

And, anyway, any thoughts of an unlikely shock were pushed to one side after 12 minutes.

Celtic had pressed, Kilmarnock cleared and blocked, but there is only so long that can go on for before the defending team concedes. After a period of possession and passing, Jonny Hayes got past Jordan Jones inside the box and the Kilmarnock winger was clumsy with a challenge.

Referee Alan Muir sought the advice of assistant Frank Connor, who shares his name with a famous Celt, and a penalty was correctly awarded. Leigh Griffiths has not always been great from 12 yards but this time smashed the ball low past Jamie MacDonald with unwavering confidence.

That lead was doubled before long. A Griffiths corner, on 22 minutes, was met by young Ralston, the only one who really wanted to get to the ball, which he powerfully headed into the net from eight yards.

Read more: Brendan Rodgers: Kieran Tierney was born to be Celtic captain

Moments later, Griffiths and Tom Rogic exchanged passes on the edge of the box and only strong hands from Kilmarnock keeper McDonald prevented Celtic’s in-form striker from adding to his total.

The kettle which had just been put on hadn’t even boiled when Griffiths made it 3-0.

Celtic’s No 9 who, it must be said looks better than ever, perfectly timed his run to get onto a superb Tierney pass over the top and with Kilmarnock’s defence in his wake, Griffiths almost arrogantly sent the ball along the grass and into the goal.

That’s his 89th goal for the Parkhead club. That is some going.

Although, Griffiths then put a black mark against his name when Gordan Greer bewilderingly gave away possession to him which allowed his opponent a clean run into the box. He should have squared to give Jonny Hayes a tap-in, it would have been the Irishman’s first Celtic goal, choose to shoot and McDonald saved.

On the touchline, Rodgers didn’t hide that such selfishness did not impress him.

Kouassi took a kick and had to go off on 38 minutes, it looked serious at the time, and he was replaced by Olivier Ntcham, Celtic’s big summer signing. If anything, as if there is one thing, which highlights the chasm it’s that substitution.

As one wag, a Kilmarnock fan, said on Twitter; “Killie did well not to concede at half-time.”

Read more: Brendan Rodgers: Kieran Tierney was born to be Celtic captain

While it’s not asking a lot for a top tier team to put up more of a fight against such a young Celtic team, it was also difficult not to feel sorry for the Kilmarnock players. They didn’t cheat their manager, they were simply utterly outclassed in every conceivable way.

Only a fine save by McDonald, who actually had a good game, four minutes after the break kept it at three. Great play by left-back Miller, which included a nutmeg on Grey Taylor, set up Stuart Armstrong and his low show was heading for the bottom corner only for the overwork Kilmarnock keeper to get his fingers to the ball.

Next to have a go was Ntcham whose effort from outside the area was saved. Rogic and Armstrong has shots blocked. The visitors to Glasgow would have taken the full-time long before the 90 minutes were up.

Griffiths got just over an hour, James Forrest was his replacement, and if he can stay fit then another 40-goal season is possible.

And then came a very special moment.

On 64 minutes, captain Tierney collected the ball the best part of 40 yards and took on a shot which flew with force and spin, and into the top corner of McDonald’s net. It really was some strike.

Armstrong was next to score, tapping home a Ralston cross from close range. There was still almost 20 minutes to go. The champions, however, showed some mercy.

Celtic have not lost a domestic fixture at Celtic Park since December 2015, when Motherwell beat them 2-1. They have won 31 out of 35 since then. As things stand, it’s close to impossible to see anyone doing anything about this.