It was perhaps apt that former Celtic goalkeeper Joe Hart was in the TNT Sports commentary box for Brendan Rodgers' side's sensational 3-1 Champions League league phase win over RB Leipzig.

There is wonderful footage of Hart not long after the ex-Manchester City and England goalkeeper had signed for Celtic when he was pictured on his summer holiday and in a moment of high jinx he was asked to sing a club song by a member of the public who also wanted a video selfie.

Hart immediately belted out the ditty: "Callum, Callum McGregor, there's no one better. He's like me and you. He loves Celtic too."

The clip went viral as Hart paid homage to his new skipper. He was at it again on Tuesday as Hart witnessed McGregor produce a European display for the ages.

McGregor was the driving force behind Celtic's magnificent win that propelled them up to 13th (at the time) in the table with seven points from four matches. The Celtic captain was class and composure personified on a night when Celtic's ball retention, game management and bravery had to be seen to be believed.

The 31-year-old put in a world-class master class in midfield and he would not looked out of place if he had been strutting his stuff in the Borussia Dortmund, Atalanta, or RB Leipzig engine room. He wasn't though and he isn't. He plays for Celtic and he put in a true captain's performance. Celtic are lucky to have him.

He always seemed to be available for a pass, he was constantly cajoling and talking to his players telling them when and what areas to press in. He dominated possession. He carried out the manager's instruction to the letter of the law.

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Remember, the manager said in the build-up to this match against the team currently occupying 2nd position in the Bundesliga table: "We have to be educated in our pressures."

Nobody was more educated than McGregor who imparted his manager's wisdom and knowledge to every Celtic player who took to the field against RB Leipzig.

The credit and plaudits will all be reserved for the likes of goal heroes Nicolas Kuhn and Reo Hatate. McGregor is the consummate professional and ultimate team player and he won't mind that but if he doesn't function to the world-class level that he did on a special European night for Celtic then the rest doesn't happen. It is as simple as that.

It was arguably McGregor's best-ever game in a Celtic jersey. It certainly was his best-ever game at the elite club level of European football. He was for want of a better word - imperious.

How's this for a statistical breakdown of the skipper's display? He completed 76 out of 78 passes, played 40 forward passes, and won four out of four ground duels and two out of two tackles. McGregor also completed one out-of-one dribble and one out-of-one long ball was successful. He won his only aerial duel and created one key chance. He had one shot at goal and he wasn't disposed once or gave away any fouls.

Hart appreciated it more than most as he watched one of the game's greatest midfield conductors in Celtic's history create a symphony against a real European heavyweight. It was music to Rodgers's and Hart's ears. It was certainly a performance you could have set to music.

It was a sublime display. At one point in proceedings, Hart opined: "Callum McGregor is running the show." He was not wrong. The role McGregor has played since 'Captain...Leader...Legend' that is Scott Brown abdicated the throne has been nothing but exemplary and outstanding.

(Image: Social Media) McGregor has been taken for granted at times in his Celtic career. He has set an abnormally high bar. If there is ever a debate about the best Celtic players of the 21st century then McGregor has to figure high in the conversation.

There will always be critics of McGregor. It comes with the territory at Celtic but what a legacy he will leave the football club when he finally decides to call it a day. At this rate, the 31-year-old can go on for a few years yet.

McGregor is the midfield maestro who probably won't ever be appreciated fully until he is gone. He is a wonderful gifted technician and a fantastic footballer.

BBC Five Live radio pundit, Pat Nevin, labelled McGregor's display against Marco Rose's men as a nine-and-a-half out of ten calling the Celtic man 'extraordinary'. It was a display of epic proportions. It showed once and for all that Celtic under Rodgers playing his style of play with McGregor the fulcrum and the beating heart of the team can be successful in the biggest arena in club football.

The back-to-back displays against Atalanta in Bergamo and RB Leipzig at Parkhead are evidence if any was needed that Celtic belong at the elite level of Champions League football.

Rodgers knows it. McGregor knows it. It was McGregor who famously said: "We have a responsibility to this club, to the badge every time we set foot on that pitch we give absolutely everything and that's what I want from the players and the club."

It's as inspirational a quote as you can get from a born leader of men. Once in every lifetime comes a love like this. The Celtic supporters should love McGregor whilst they still can. He may not be the 'Young One' for very long but once in every lifetime, a generational footballer comes along.

McGregor is the living embodiment of that in a Celtic jersey. He has borne the responsibility of the Celtic captain's armband with aplomb. He has and continues to give everything for the club badge every time he sets foot on the pitch. He is one of Celtic's true unsung heroes. He remains Celtic's unfashionable superstar.

In the words of Joe Hart: 'Callum, Callum McGregor. There's no one better...'

That's a football fact. Repeat to fade.