Police had to intervene after an ill-tempered end to Atletico Madrid's 0-0 draw with Manchester City in their Champions League quarterfinal second leg spilled over into a post-match confrontation in the tunnel.
City will face Real Madrid in the semifinals after holding off a late rally from a much-improved Atletico in the second half at the Wanda Metropolitano on Wednesday to progress 1-0 on aggregate.
Tensions boiled over in the 91st minute when Atletico defender Felipe was sent off for a challenge on Phil Foden, sparking a touchline brawl which continued in the tunnel after the full-time whistle.
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TV images showed Stefan Savic trying to confront Jack Grealish, having earlier been pictured pulling the City player's hair in the melee after Felipe's red card. Substitute Sime Vrsaljko had to be restrained by Atletico coaching staff, and Kyle Walker was held back by goalkeeper Ederson, before police officers moved in to restore order.
"The game can make you mad like that, when you're putting them under pressure and creating chances, and they're going down, wasting time," Atletico captain Koke said, when asked about the red card and the fracas that followed. "It's football. We often get criticised for that, let's see what people think about it today."
Atletico's players were angered by what they felt were attempts by City to run down the clock as they protected a 1-0 first leg lead.
"In a tense game like that, it can happen," Atleti goalkeeper Jan Oblak said. "People came on from the bench, there are a lot of nerves, it's normal that there's pushing and some bad words said. What happens in a game, stays there. It was good for City, it wasted a bit of time."
However, City defender Aymeric Laporte hit back, saying: "Who were wasting time were their team, getting into absurd fights.
"We already know how they are and they always do the same. It's always ugly to see these fights, a lot of fuss is made with little. I think it was bad for them because they were in their best moment in the game."
Pep Guardiola refused to answer questions about time-wasting, but City midfielder Rodri admitted that there are times when it is necessary.
"When you are locked behind and when there are five to 10 minutes left, we have to play with other weapons," Rodri said.
"I am not in favour of doing it throughout the game, but on occasions. What stays in the field stays there. It's a game with a lot of pressure and I don't really know what happened to Felipe, but it's not pleasant."
Both Oblak and manager Diego Simeone said they had not seen what happened in the tunnel, as they had remained out on the pitch after the game to thank Atletico's fans for their support.
"I didn't see it. I was with the players, applauding the fans," Simeone said in his postmatch news conference. "When I went up the stairs [in the tunnel], nobody was there."
Simeone denied that he had aimed ironic applause at City's bench and opposite number Guardiola in added time -- saying: "I didn't applaud the opposition bench, I applauded our fans," -- but still appeared irked by Guardiola's comments on Atletico's defensive tactics after the first leg.
"Often, people with a large vocabulary are very intelligent, and they manage to praise you with disrespect," Simeone said. "But those of us who maybe have a smaller vocabulary, we're not so stupid.
"Football has a lot of facets. I won't give my opinion on how the opponent behaved. We'll focus on us, playing against maybe the best team in the world, and realising we could compete. But that doesn't make me happy, the only thing that makes me happy is winning."