Football fans noticed the linesman's bizarre antics during Portugal vs Slovenia on Monday night.
Cristiano Ronaldo was the talk of the town during the Euro 2024 round of 16 clash.
The five-time Ballon d'Or winner cut a frustrated figure after spurning a number of chances and seeing an extra time penalty saved by Jan Oblak, ultimately leading to him in tears.
He recovered to score the first spot-kick in the shoot-out, where Diogo Costa proved to be the hero with a historic three saves in a row.
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But while the spotlight was firmly on Ronaldo, many viewers watching on BBC One picked up on what was going on with the assistant referee on the far side.
Italians Ciro Carbone and Alessandro Giallatini both served as linesmen for the game, with Daniele Orsato the man in the middle.
Linesmen are of course required to be on the side of the pitch and keep up with play, but one of the officials went to extreme lengths.
On multiple occasions, the linesman was seen on the pitch with his flag in hand, having accidentally crept onto the playing turf.
And there was reaction aplenty on social media, who couldn't help but spot it.
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One wrote: "You were all watching the Portugal match for Ronaldo, but didn't see that this linesman kept running on the pitch the whole match!"
A second said: "The most interesting part of Portugal vs Slovenia is when the linesman literally enter the pitch."
A third added: "Linesman on the far side repeatedly encroaching on the pitch whenever the ball goes in the Portugal box.
Another user commented: "I can’t concentrate in the Portugal game because the linesman is a nutter who can’t stay on the line. Man’s all over the place."
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A final person asked: "Does the linesman know he supposed to be behind the line in the Portugal Slovenia game?"
Portugal return to action on Friday when they take on France in the quarter final in Hamburg.
Josh Lawless