Police were forced to intervene when Atletico Madrid and Manchester City players clashed in the tunnel after their Champions League quarterfinal second leg tie ended in controversy on Wednesday.
According to the Athletic, UEFA are likely to pursue disciplinary action in relation to the events which ensued after a tense 12 minutes' worth of injury time laden with fouls and yellow and red cards.
As broadcast footage from French television shows, Stefan Savic and Jack Grealish ran down the tunnel arguing with each other before Atletico defender Sime Vrsjalko could be seen throwing something at City staff including Aymeric Laporte and apparently spitting at them after the tense 0-0 draw which was enough for the English outfit to book a semifinal date with Real Madrid.
Vrsjalko and City right back Kyle Walker had to be restrained from getting at each other, with police officers then appearing to intervene as Stefan Savic was once more the protagonist following run-ins with Grealish, Phil Foden and Raheem Sterling earlier in the evening.
Asked about the incident in their post-match interviews, however, City boss Pep Guardiola stated that he had "nothing to say" while his opposite number Diego Simeone claimed not to have been present and had therefore not seen anything.
A nail-biting 0-0 draw resulted in the Premier League Champions advancing to the semifinals of the competition for the third time in their history by winning 1-0 on aggregate thanks to Kevin De Bruyne's 70th-minute goal at the Etihad last week.
In a smart way to approach the tie in front of a packed, boisterous crowd at the Wanda Metropolitano, though, City beat Atleti at their own game by engaging in the Dark Arts and adopting a wide range of provocative tactics such as exaggerating the seriousness of fouls, lying on the floor for extended periods, and seemingly running down the clock.
By the 89th minute, with the game slipping out of the defending La Liga champions' grasp, Felipe saw red when picking up a second yellow for a touchline foul on Phil Foden which enraged Savic.
Feeling that the England international was playacting, the Montenegrin dragged Foden back onto the pitch which sparked a mass brawl between the two sides.
Continuing their previous animosity from the first leg, substitute Grealish allegedly called Savic a "c**t" as the ex-City man grabbed Grealish by the hair and then headbutted Raheem Sterling.
Atleti coach Simeone was booked alongside a string of other players such as Nathan Ake and Savic, and after 12 minutes' worth of stoppage time, the melee then continued in the tunnel after Simeone argued with City left back Joao Cancelo and Guardiola was pelted with bottles as he attempted to head to the changing room.
After the first leg, Guardiola had taken a dig at Atletico by remarking that it has been difficult to attack a team that defends with two lines of five "ever since prehistory."
Probed on whether the Catalan had shown him and his team a lack of respect, Simeone insisted that he doesn't "have to offer an opinion about whether someone is speaking well [of us] or not."
"Often, those who are very eloquent are very intelligent and have a way of praising you dismissively. But those of us who maybe have less eloquence are not stupid," the Argentine added.
Guardiola insisted that has "only ever had good words to say" about the world's highest paid coach, though.
"He can play however he wants, of course. I would never say otherwise. All I said was that it is very hard [to play against a 5-5-0]. And they know how to do that better than anyone in the world."
"Atletico were absolutely brilliant," Guardiola complimented the Rojiblancos. "I don’t like playing that way at all but this team playing like his with their people behind them are almost unstoppable. All I said was that when a team plays that way very, very well, it’s very difficult. Nothing else.
"Don’t be mistaken, I never criticized Atletico," Guardiola continued. "They pushed us back, we forgot how to play. That’s to their credit. We’re celebrating going through but after that second half we could be out. We were in big, big trouble. They had chances to score, but they didn’t in the end."
With two matches now set up with Atleti's cross-city rivals and 13-time winners Real Madrid, which offer City the chance to reach a second final in two years after last season's loss to Chelsea in Porto, Guardiola then predicted that his charges "don't have any chance" if they play as they did in the second half.
City and Real Madrid will meet in the first leg at the Etihad on April 26, with the return leg played at the Bernabeu on May 4 after Los Blancos saw off holders Chelsea 5-4 on aggregate in a thrilling encounter in the Spanish capital on Tuesday.