It was the moment at which Juventus realised there might be a downside to 'The deal of the century'.
Cristiano Ronaldo had been signed to lead the Bianconeri to Champions League glory.
However, just 30 minutes into his first European outing for the club, he was in tears, and disbelief, at having been dismissed for running his fingers through the hair of Valencia defender Jeison Murillo.
The red card may have been farcical but Ronaldo's reaction was no laughing matter for Juventus.
This was a surprising and worrying show of raw emotion, one which suggested that Ronaldo was so tightly wound, so desperate to achieve his stated objective, that the slightest setback was too much to take.
His last-minute decision to snub the UEFA awards ceremony in August after learning he had been beaten to the Player of the Year award by Luka Modric was taken as further evidence that Ronaldo was a prima donna incapable of dealing with either ejection or rejection.
It was not as if Juve didn't know that Ronaldo was – and is – a sensitive character, his time at former club Real Madrid having been punctuated by sudden emotional outbursts, both on and off the field.
His mood was always a topic of huge debate.
He was seen several times berating other team-mates for failing to pass him the ball – he even once reacted angrily to a Gareth Bale goal – while he infamously attributed Real's derby defeat to Atletico Madrid in 2016 to the quality of his supporting cast.
"If we were all at my level, maybe we would be leaders," Ronaldo argued at the time.
"I don't want to disrespect anyone, but when the best players aren't available it's harder to win. I like to play with Karim [Benzema], with [Gareth] Bale, with Marcelo.
"I'm not saying the others like Lucas [Vazquez], Jese and [Mateo] Kovacic are not good players – they are very good players – but it's not the same."
The fear was, then, that when the going got tough for Juve, Ronaldo would start going after team-mates with less impressive resumes.
The Portuguese, though, has quickly emerged as one of the leaders in the Juventus dressing room, and not because of his reputation, but because of his actions, his spirit of inclusion, as most recently underlined by his tribute to the benched Paulo Dybala after netting against Sassuolo last weekend.
Even after arriving, Ronaldo made a point of saying that Juventus, as a club, feels "like a family; everybody is friendly here".
Sergio Ramos insisted it was no different in Madrid: "Here we have always felt like a family, so I don't know what he was talking about.
"We have had lots of success, which is because we are a family and he was part of that family."
Ramos subsequently inferred, though, that Ronaldo had been Real's spoilt child.
"He does what he wants" was the defender's reaction to Ronaldo's awards snub.
"The mindset we have here," the Madrid captain also argued, "is more important than any individuals in the team."
Ronaldo, though, has proven a true team player in Turin.
Despite the predictable hysteria surrounding his arrival, he entered the dressing room without any heirs or graces.
He humbly asked team-mates for recommendations for restaurants and places of interest, and made a point of immersing himself in the history of the club.
There was no sense of entitlement or suggestion that he had come to Italy to take it easy.
Colleagues were left blown away by his work ethic.
"It’s remarkable, Ronaldo trains and plays like he’s my age," enthused the 24-year-old Joao Cancelo.
Douglas Costa added, "It is impossible to keep up with Cristiano Ronaldo in training. When we arrive, he is already training; when we leave, he is still training.
"I have never seen a player like that."
He has also surprised with his selflessness, often appearing to derive as much joy from creating a goal as scoring one.
Almost inevitably, he is leading the race for the Capocannoniere award, with 18 goals.
However, even when he was struggling to get off the mark at the start of the season, there was no sulking – only smiles – when others were netting ahead of him.
Indeed, he even afforded himself a laugh when he somehow failed to convert from a couple of yards out against Lazio on matchday two, inadvertently setting up Mario Mandzukic for a goal in the process.
The impression is that Ronaldo and Juve is a mutually beneficial relationship in which they are bringing out the best in one another.
Coach Massimiliano Allegri has hailed him as "a leader", while midfielder Blaise Matuidi says he is inspiring all of those around him.
"He makes the team grow and also his team-mates stronger," the World Cup winner stated.
Club captain Giorgio Chiellini has even admitted that he is learning a great deal from the five-time Ballon d'Or winner.
"I’m a curious person, I’m a good observer and having Ronaldo near me is interesting," the defender explained.
"He’s like [Usain] Bolt and [Roger] Federer and knowing the habits of those who have an extra gear helps.
"It’s not to imitate him but rather to broaden my horizons."
Ronaldo may well be one of the most well-known sportsmen on the planet but it seems that, thanks to his move to Juve, we are now seeing a whole new side of him.