Porto were 1-0 up in their Primeira Liga match away at Vitoria, when a fan broke onto the pitch and proceeded to aim kicks at multiple players.
It was a grim night at the Estadio Dom Afonso Henriques that detailed the escalating problem with regards to fan behaviour across Europe.
The incident
The visitors were 1-0 up on the night, courtesy of a Mehdi Taremi penalty, and were simply looking to see out the game in its closing stages.
However, the result became a secondary concern when an unknown spectator calmly marched onto the pitch and approached Vitoria captain Rochinha.
Initially with his arms outstretched, it seemed like he was going in to hug his favourite player, yet at the last second he swung an aggressive kick in his direction, connecting with Rochinha's lower leg.
Straight after the incident, he went after Vitoria winger Geny Catamo, but luckily the Mozambique international managed to jump out of the way in time to avoid the vicious strike.
Chaos ensued as players, the Vitoria manager and the referee all charged over to try and break up the altercation, before the pitch invader was restrained and dragged off the field.
A truly bizarre turn of events! Play did eventually resume and Porto went on to see out the narrow victory, extending their lead at the top of the Primera Liga to six-points with just five games remaining.
Reaction to the incident
Fans and viewers watched on in shock as the chaos unfolded in front of them, which of course prompted many to voice their opinions on social media.
One fan tweeted: "It's quite amazing how easily he managed to get onto the pitch."
With another following up: "The guy literally walks onto the pitch as if he's lost!"
They couldn't be more right, a final fan tweeted: "The security is scarily lax."
It's unknown who the fan actually supported but the fact that he was able to march onto the pitch with a backpack on, totally uncontested, ought to be a real safety concern for players and spectators alike.
A lifetime ban will surely be in order for the fan in question, although, a full investigation into the incident and the security around Portuguese stadiums needs to be the next port of call.