"We're glad you were able to see the GOAT (greatest of all time) on your pitch," the Blaugrana wrote on their Twitter feed.
Juve's social media team replied, "You probably looked it up wrong in the dictionary. We'll bring the right one at Camp Nou."
It would make for an easy narrative to say that Barca won because they had their "GOAT" while Juve were without theirs, Cristiano Ronaldo.
And, certainly, in the era of knee-jerk reactions, a Champions League clash between two heavyweights of the European game was always going to provide plenty of hot takes.
Christian Vieri, for example, was so bewitched by what he saw from Messi that he predicted that a side coming off a chastening Clasico defeat at Camp Nou could now go the rest of the season unbeaten.
"It's impossible the way they played. Every game is different but the Barcelona I and everyone else saw was just incredible.
"When you've got a No.10 like that, it's just crazy. Messi is a magician, he's the Harry Potter of soccer and when he stops playing, I'm throwing my TVs away.
"I'm not going to work no more on TV, I'm going to watch Netflix, that's it, because when he stops, there'll be nothing else to watch."
While Vieri was worried about football's Messi-less future, Fabio Capello was more concerned about the current state of the Italian game.
"Juve suffered a lot," a visibly concerned Capello said on Sky Sport Italia. "They played against a Barcelona in crisis and yet I was struck by the difference in quality, their superiority to a top Italian team.
"What impressed me most was how quick Barcelona were. They could have scored eight goals tonight and this is what makes me doubt what we have here at home in Italy."
It is certainly a little bit too early for such general pessimism on the strength of Serie A – all four of its Champions League participants remain well placed to qualify for the last 16 – but there are understandable concerns over Juve's condition.
Even accounting for the absence for several key players, the Bianconeri were abysmal against Barca, failing to register a single shot on target.
Alvaro Morata had three 'goals' disallowed for offside – correctly – but there was nothing unfortunate about Juve's defeat. As both Vieri and Capello pointed out, the final scoreline flattered the home side.
This was undeniably Barca's best performance of the season so far, and Messi's too.
It would be too convenient to argue that Josep Maria Bartomeu's resignation on the eve of the game had played a pivotal role in the Argentine's excellence.
After all, he had shown his quality – and no shortage of effort in Saturday's Clasico defeat. Messi’s wildly contrasting fortunes in Turin were merely based on the quality of the opposition.
Madrid endured plenty of nervy moments against Barca but they had a game plan, stuck to it and eventually reaped the rewards.
Juve, though, did not even come close to impose themselves on the game. They were overwhelmed right from the kick-off.
The idea was to spread out the Barca back four and isolate Sergi Roberto. However, they succeeded only in spreading themselves too thinly across the pitch.
Indeed, it was staggering just how easily Barca were able to break through Juve's defensive lines – and often with just two or three passes.
The hosts were static and far too narrow, allowing Sergi Roberto but particularly Jordi Alba to attack at will down the flanks. It was no coincidence that the Barca left-back made more successful passes (96) than any other player on the pitch.
In addition, they only man who had as many touches as Alba (110) was Messi, who created the first goal for Ousmane Dembele with a delightful switch of the play, and scored the second from the penalty spot.
While Paulo Dybala was marked out of the game, with Barca doubling up on the Argentina international every time he got the ball, Messi was essentially given the freedom of the pitch, which is always a recipe for disaster for any opponent.
The finger of blame was, unsurprisingly, pointed at Pirlo immediately after a shockingly one-sided affair.
Why was Federico Chiesa – the man charged with tormenting Sergi Roberto – so often ignored by his team-mates?
Why did Juve move the ball so slowly? How did they manage to play without any aggression, as Danilo admitted, and yet still pick up a third red card in six games?
Pirlo understandably pointed to the fact that Giorgio Chiellini, Ronaldo and Matthijs de Ligt were all unavailable for selection.
“I hope to have more players back soon, because I don’t have many options and those I start end up having to play almost 90 minutes twice a week," he told Sky. "That’s not easy for them, especially when they are young and inexperienced."
The good news for the rookie coach is that there is an acceptance at board level that the rejuvenation of the squad was always going to affect results.
"It was easy to predict difficulties, as we changed a great deal within the squad and on the bench, so not having much of a pre-season to perform tests, we’re experimenting during the season,” Juve director Pavel Nedved told Sky.
"These are not excuses – they are statements of fact."
And Nedved is right: Pirlo should only be judged when he has had more time to work with his squad and has all of his best players at his disposal.
However, it is worth noting that Nedved made that plea for patience before the game, and said of Pirlo's project "We'll see how we are doing tonight."
Not very well is the obvious conclusion. As Danilo admitted afterwards, not once this season have Juve played well for an entire match. On Tuesday night, though, they played terribly for a full 90 minutes.
Ronaldo's imminent return will obviously add a whole other dimension to the attack, while Chiellini and De Ligt will undoubtedly shore up the defence.
There are obvious tactical issues at play, too, though. Too many players are struggling with Pirlo's hybrid 3-2-5/3-4-3 formation, meaning he has to ask himself: does he presently have the right personnel to play this system?
He needs to be as adaptable as he is asking his players to be and yet, the last thing he wants to do is make the same mistake as his predecessor, Maurizio Sarri, by compromising on his footballing philosophy.
It is quite the conundrum. And there is no easy solution. There is no quick fix.
Unlike Messi, Pirlo has no magic wand.