Barcelona thrashed Valencia 5-0 at the Mestalla to move top of the Spanish league on their own.
Hansi Flick's side started strongly at the Mestalla, imposing their style from the outset against a sluggish Valencia.
The opener arrived inside five minutes. Lamine Yamal steered the ball home with the outside of his boot after a wonderful pass from Fermin Lopez.
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Yamal found the net again two minutes later, but VAR chalked it off for offside on review.
Ruling it out took several minutes, a surprise given that semi-automated offside is one of this season's new features in the Spanish league.
Flick vented his frustration at the fourth official as Barcelona's brilliant start ground to a halt, the players left waiting to learn whether the flag would go up.
Officials flagged Lamine offside by a matter of millimetres, though former referee Iturralde Gonzalez was unconvinced during the live broadcast of the "Carrusel Deportivo" programme on "Cadena SER" radio.
He said: "It's very close, and the image we have is not the best. What I don't understand is that we have an automated system for the ball's electronic chip technology, and the time it takes is not normal."
He then pointed to the reason for the referee's delay: "The delay must be due to a system malfunction, and that they are redrawing the lines manually. Otherwise, it makes no sense."
He concluded by saying: "But this offside is easy for the device, because the players are separated."
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