Sometimes it boils over into something raw, messy and unforgettable, like what we saw after Virgil van Dijk's late header sealed Liverpool's dramatic 3-2 victory over their Spanish opponents.
History is littered with moments where the divide between players and fans collapsed in ugly fashion, producing the sort of headlines even the most expensive of PR teams can't spin away.
Here, Flashscore looks back at how combustible the relationship between crowd and pitch can be.
Eric Cantona at Selhurst Park, 1995
Nothing before or since has quite matched the sight of Eric Cantona, in that classic all-black Manchester United away kit, launching himself boots-first into a supporter at Selhurst Park.
Moments earlier, he had been dismissed for kicking Crystal Palace defender Richard Shaw. On his walk to the tunnel, he was met with goading from Matthew Simmons, a Palace fan whose words ultimately proved incendiary.
Cantona responded by launching into the stands with a shocking kung-fu kick and flurry of punches.
The consequences were severe for the Frenchman: a nine-month ban, a fine and community service.
Yet the incident also crystallised Cantona's cult status, his subsequent press conference musing about seagulls and trawlers sealing the mythology.
It was a collision between genius and volatility that Premier League football often prides itself on when remembering its icons.
Jamie Carragher on the M62, 2018
Few reputations in English football were as steady as Jamie Carragher's until March 2018, when a motorway altercation reduced a promising punditry career to a moment of madness.
After Liverpool had lost 2-1 at Old Trafford, Carragher was mocked from a passing car while driving home on the M62 motorway.
He reacted in the worst possible way, spitting through his window and hitting a 14-year-old girl.
The video footage went viral, prompting his suspension from Sky Sports and universal condemnation.
Carragher apologised repeatedly on every conceivable news channel - and with genuine sorrow - but the (saliva) stain remains.
For a player once defined by steely toughness and composure, the lapse was as jarring as it was indefensible - a bit like one of his many own goals from his playing days.
Eric Dier marches into the stands, 2020
Eric Dier's dash into the Tottenham Hotspur Stadium seats after their FA Cup penalty shootout defeat to Norwich was less an act of aggression than instinctive protection.
Seeing his brother targeted by abusive supporters, he charged over advertising hoardings and stormed into the rows of plastic seating.
Security intervened before anything physical occurred, but the image of a Premier League footballer in full kit and studs clambering into the stands was extraordinary.
The FA handed him a four-match ban. Then-Tottenham manager Jose Mourinho defended the player's impulse, framing it as family loyalty.
Dier's actions, reckless though they were, spoke to footballers' human vulnerability in the face of personal provocation. A reminder that players are still human beings, ultimately.
Mario Balotelli and the digital mob, 2014
If the terraces are combustible, social media can be like letting off a firework in a washing machine.
Mario Balotelli's fraught relationship with English football was never far from the headlines, but in 2014, it collided directly with online abuse.
Having posted what he insisted was an anti-racism message - loosely following in the footsteps of megastars such as Neymar, Luis Suarez and Sergio Aguero after a banana was thrown at Dani Alves during a Barcelona match in Spain - he was deluged with vitriol over perceived stereotypes in the post, which featured derogatory references to black, Mexican and Jewish people.
True to form, Balotelli did not disengage but retaliated, challenging detractors to confront him in person, and telling others to "shut up because my mother is Jewish".
The FA eventually imposed a fine and a one-match ban, while the episode demonstrated that conflict between players and fans no longer needed to occur in real life; it can also play out on Instagram feeds and Twitter timelines.
Paolo Di Canio and the Southampton hotel fracas, 2013
When Paolo Di Canio was managing Sunderland, he found himself in an unlikely confrontation, not in a stadium but in a hotel corridor.
As he and his staff returned late at night before a match against Southampton, they encountered a group of inebriated Saints supporters attending a wedding party.
Words were exchanged, gestures made, and police summoned.
Ever the showman, Di Canio later described it as "a fun moment", dismissing claims of a brawl but admitting the tension was real.
"They said, 'We are going to win, Rickie Lambert is going to score,' and Fabrizio (Di Canio's assistant) said, 'No, tomorrow we're going to win.' It finished like this. No footballers, no fight." Naturally, it finished 1-1.
Still, the story was pure Di Canio in all his often questionable glory: part menace, part comedy, part theatre.
Even far from the pitch or a referee, he found himself locked in conflict with the crowd.