Exactly 4,632 days had passed since the first time Cristiano Ronaldo turned up at the Camp Nou and found that there was an impish little Barca-coloured magician in the opposition ranks. A fly in his ointment.

That was Manchester United en route to winning the Champions League in 2008 -- the first leg of the semifinal.

Unlike December 2020, this old stadium was utterly packed to the rafters back then for the Camp Nou's first Lionel Messi-Ronaldo instalment -- 95,949 rabidly passionate fans. Those were the days.

Just like December 2020, however, Barcelona were in the mud. Knee deep in fact.

Out of the Copa del Rey and in the midst of a five game winless run, 11 points behind the champions-elect Real Madrid and with a manager who was a veteran of that Dutch European Championship winning team in 1988.

Frank Rijkaard back then, Ronald Koeman today. Teammates in the spectacular win over the U.S.S.R. when the Netherlands won their first major trophy, united by overseeing Barcelona turbulence and failure now.

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Just like December 2020, in April 2008, all those 662 weeks ago, Ronaldo had an early penalty.

Three minutes into that semifinal, and 13 minutes into this one-sided clash which definitely served to put Ronaldo's Juve through as group winners but might also have served as the last club match between these two behemoth footballers who have dominated the scene, and our debate, for the last 16 years.

Back in 2008, Ronaldo skewed his penalty wide of the goal frame.

Gifted here the late-career chance to make amends for that rare failure, Juventus' Portuguese superstar smashed the ball twice past Barca keeper Marc-Andre ter Stegen, taking very little heed of the fact that the first spot kick was one of the weakest decisions with which he's ever been blessed.

Not his fault. But this was a comedy. When Ronald Araujo leaned shoulder to shoulder with Ronaldo, Juve's No. 7 didn't even claim a foul, and when the referee blew for a spot kick it was comedy itself to see the shocked double-take which it caused in Barcelona's ranks. Ronaldo just shrugged in a gesture which said: "Whatever ref, I'll take it!"

So while Ronaldo took his tally of converted penalties when he's been playing against Messi to five, the Argentinian could do no more than watch. Helplessly. Frustratedly. No doubt angrily.

Of course nobody knows whether this was the swansong for this most absorbing, polemic and wonderful rivalry between the silky Messi and the powerful Ronaldo.

But I can say this definitively: If this is the last time they meet on the pitch (which, personally, I doubt) then this will have been a poor way to remember the rivalry.

In Barca, Juve didn't really have a rival worthy of the name, or the of the occasion if this was a curtain call to the Messi-Ronaldo show of shows. Ronaldo played all the right notes.

Tucking away his two penalties, almost helping Leonardo Bonucci force home a fourth goal which would have sealed group victory much earlier, his trademark leap, twirl and roar celebrations were all there and we even got a nice "pally" embrace between him and the man who once drove him to distraction but to whom, over time, he's learned to show respect and even some affection.

Beyond that, there was one marvellous moment when Ronaldo, being Ronaldo, utterly refused to accept the idea that a stray Barcelona goal might help them win the group on the head to head record despite being thrashed on the night, and dashed back into the Juve penalty area to dole out tackles and clearances. That was a sight and a half.

But you could argue that if your vista was skewed away from the scoreline, the team performances, which side won the big prize (the answers so that you don't have to phone a friend or ask the audience are: Juve, Juve and Juve) that Messi was the more interesting and "involved" participant in this game, which smashed Barcelona's seven and a half year unbeaten home run in this competition.

Messi is in a slump. His form is sluggish, the team around him is decayed and the reinforcements are young and eager, not street-wise and battle-ready.

Although he's given Koeman zero problems with his manner or attitude in training, Messi is nonetheless pretty disgusted that for one reason or another he didn't manage to give the slip to his markers in August.

By which I mean the now departed president and board of FC Barcelona who were staunch in their refusal to let him join Manchester City on a free, despite having promised such a thing, but less staunch in staying on to finish their mandate when they fancied doing a runner.

Yet on this potential bookend to what has been an uproarious and unforgettable 36 match (including this Juve win) head-to-head sequence between two men who go far beyond the status of football legends and stand on a pantheon of post war sporting greats in any discipline, Messi woke up.

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He's been too sleepy too long. The effects of this strangest of calendar years where then body clock of almost all team-athletes is all to pot, then the effects of having run his legs off non-stop for years and years as he leaves behind his Peter Pan persona and turns 33, well those effects are pretty noticeable now.

So it wasn't possible for this, as many neutral spectators would have loved, to turn into a blow for blow slugfest between the two stellar participants.

One where Ronaldo was at the spearhead of an apparently indomitable invading Italian force, but Messi was the individual partisan who might lead and inspire some rag-tag and bobtail Camp Nou resistance to an unlikely result. That sort of Hollywood script.

After the match, Ronaldo said: "Scoring here is always special for me. With Messi we have shared the last 12, 13 years of our lives. It's always good to face him. Obviously people speak of our rivalry but for me it is always a privilege to face him and obviously I'm happy to score when I face him.

"I feel very good, goals are important but I want to continue working like this because it's not easy to keep the same standards all the time."

But, no. This was a team victory. In fact a squad one. But back to that in a minute.

Notwithstanding all that, Messi worked his little socks off.

More pressing, more finding space, better wall-passes, and an emerging side-show which diverted the spotlights form what was supposed to be the main show.

When he walked off at the end, Messi had changed strips not with Cristiano, who was by then a couple of minutes into his warm Juve polar-anorak having been subbed off by manager Andrea Pirlo with only added time left. No, Messi chose Gianluigi Buffon.

And there was a reason. On a night which the headline makers yearned to title "Messi vs. Ronaldo Part 36!", the truly engaging battle was Messi vs. Buffon.

Over and over again Messi either stung the gloves of this Juve behemoth, who will be 43 in January, or sent him diving to either side of what would be an un-breached Juventus goal frame.

When in the first half it looked as if the otherwise sensational Weston McKennie had nudged Messi as he shot and the Barcelona players were demanding a penalty it was just dandy to see Messi looking up to Buffon with a "was it a penalty?" quizzical look, and when the giant Italian shook his head "no mate, it really wasn't" Messi gestured a little thumbs up to Juve's legendary keeper. Two greats.

A little later, as Buffon clutched the ball and jogged to the edge of his area to try and quickly re-start the play, Messi playfully tugged at his shirt from behind and Buffon didn't even stop to look -- he broke out in a grin. He knew who it was, didn't lose an iota of temper and gave Messi a little clip on the shoulder as he ran past.

That didn't stop him saving Messi's efforts on goal time and again, though. On a night when this was supposed to be Barcelona's No. 10 vs. Juve's No. 7 it was, in fact Juve's No. 77 who helped spoil the party and steal the cake.

All of which helps move the story beyond what happened here.

Messi vs. Ronaldo over the years has been a great tapestry of each of them adding superlative moments of bare-naked bravado and brilliant improvisation on top of the work their magnificent teammates produced.

They have been the two outstanding players of most of our lifetimes, no matter whether or not you had a slight preference for one or the other. Just think that 10 times in the Ballon d'Or awards since 2007 one of these two has pipped the other by a single position, usually first and second, and the last award saw Ronaldo in third and Messi first.

Back and forward the pendulum has swung but, no matter how well either did individually, it was always the case that they were playing in a unit where there was special talent, special endeavour, huge spirit and a recognition that everyone, be they fellow players or technical staff, were working to make a platform for either Ronaldo or Messi to add the finishing, winning touches.

This is not the case right now. In Ronaldo's favour, he had the ambition, the restlessness, the hunger and the ambition to reject continued life at Madrid, to risk moving to a club and a league which, compared to the last 20 years of Spanish football, could be described as moribund.

Whether you think it was the right move or not, the fact is that he's flourished. More league titles, a vast haul of goals last season, Serie A's most important footballer and now -- this.

What was wonderful to watch and I'm sure what will have given Messi pause for thought, probably even an extra impulse to leave the Camp Nou at the end of his contract was watching Juve operate around Ronaldo.

Every ball was a prisoner, they surged out of the blocks with complete and absolute belief that they could and would win by three or more clear goals. All around Ronaldo were footballers running like dervishes, passes delivered at speed, support play when a Juve man robbed the ball back -- this was a team.

They were fitter, bigger, faster and cleverer. And all the while Messi was playing with teammates that Koeman later described as looking as if they were fearful. Teammates who Antoine Griezmann later said needed to take this defeat as a a wake up call.

If we are ever to have a Messi-Ronaldo showdown which, irrespective of who wins, who scores, is fitting of the years of rivalry and the 35 direct clashes between them, then Messi has to leave Barcelona. At 33 he's not finished, he's still got masses of moments of brilliance to gift this game, with which to entertain us and via which he can get some personal satisfaction after this long run when he's been playing for a pale imitation of Barcelona.

They were bitter rivals for a while, there was mutual envy, dislike and jealousy then there was respect and, even affection. There were headers, dribbles, penalties, trophies, excellence, excitement, mutual incentive to get better, to never relax and a series of the most magical, unpredictable, world-impactful Clasicos in the history of that fixture.

It's a privilege beyond measure to have watched the rivalry unfold, to interview both of them, to see each of them behind the scenes, to be lifted from my seat by the sheer excitement of seeing things which surpassed anything I'd witness or written about before.

But now, if -- and please don't let it be -- this happens to be the end of one of sport's greatest-ever personal rivalries in its on-pitch version then perhaps Ronaldo has done Messi a huge favour: The favour of showing him that moving on, experimenting with the right "pastures new" can actually lead to greener grass, greater fun, and a proper career autumn that true greats like these two so massively deserve.

The favour came in the form of hard, bitter medicine. But if it helps cure Messi of what ails him right now then a Christmas card to Ronaldo may be in order.

Either that or an unlikely rematch in the later knockout rounds of this competition. But that's another story altogether. For now this story will have to do.