The Portuguese top-flight game between Porto and Vitoria de Guimaraes descended into chaos when a fan walked onto the pitch and attempted to kick out at two of Vitoria's players.
Mehdi Taremi had given the visitors a 1-0 lead from the penalty spot, and later missed a second penalty. However, the score became secondary when the pitch invader approached Vitoria captain Rochinha, initially holding out his arms as he walked towards the 26-year-old but then appearing to kick him.
Seconds later, he attempted to take a swing at a second Vitoria player, Geny, but the winger got out of the way in time. It was far from the first notable pitch invasion in a top league this season, with an incident at Everton v Newcastle attracting attention, but it may well worry the players who were approached without any intervention from stewards or officials.
It wasn't the first time this season in which a Porto game has descended into chaos, though the reasons are very different. Back in February, a top-of-the-table clash between Sergio Conceicao's side and title rivals Sporting CP ended in a 40 man brawl, with veteran defender Pepe sent off for his part.
On this occasion, the fan walks calmly onto the pitch, rather than showing any urgency, while the referee and assistant watch on. After holding out his arms towards Rochinha, he appears to kick the player in the lower leg before approaching Geny.
Eventually, the pitch invader was restrained. By then, Vitoria boss Pepa had left the technical area and attempted to stop things escalating further, while other players rushed towards the scene of the incident.
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"It's quite amazing how easy he managed to get onto the pitch," one viewer noted. Another said "The guy literally walks onto the pitch as if he's lost".
The game eventually resumed after the interruption, with just a couple of minutes of stoppage time remaining. Porto held a 1-0 lead at the time, with their opponents a man down after the dismissal of Oscar Estupinan, and that's how things ended.
Following the victory, Porto sit six points clear of second-place Sporting with just five games remaining. The Lisbon team had put the pressure on with a 3-1 win at Tondela on Saturday, but the gap remains.
Despite the victory, Conceicao is refusing to consider the title wrapped up. "I'm always alert and very suspicious," he told the club website.
"It is in these moments that teams get distracted and troubles happen. We have to be suspicious and alert and we'll prepare well for the next game, which is at home.
"We are very focused and very focused on doing our best. We have five finals ahead of us and nothing is decided.
"We're happy with our journey so far, but it's not over yet and the hardest part is missing, which is the final part. The true champions are those who continue to work hard and focus hard on the best moments."