A refereeing expert on the disallowed Yamal goal: "This is not normal"

Barcelona secured a comprehensive 5-0 victory over Valencia at the Mestalla, moving to the top of La Liga on their own.

Hansi Flick's side started strongly at the Mestalla against a Valencia in clear decline, imposing their style from the first whistle and making the most of every opening.

The opener arrived after just five minutes, Lamine Yamal cleverly steering the ball home with the outside of his foot following a superb pass from Fermin Lopez.

Two minutes later, Yamal found the net again. VAR ruled it out, flagging an offside on review.

The disallowed goal took several minutes to confirm, which is surprising given that semi-automated offside is one of La Liga's new features this season.

Flick vented his frustration to the fourth official as Barcelona's brilliant start ground to a halt, the players left waiting to learn whether the flag would stand.

Millimetres decided the call against Lamine, though former referee Iturralde Gonzalez was not convinced during the live broadcast of "Carrusel Deportivo" on "Cadena SER" radio.

He said: "It is very close, and the image we have is not the best. What I do not understand is that we have an automated system for the electronic chip technology in the ball, and the time it takes is not normal."

He then pointed to the reason for the referee's delay in disallowing the goal: "The delay must be due to a fault in the system, and that they are redrawing the lines manually. Otherwise, it makes no sense."

His verdict was blunt: "But this offside is easy for the machine, because the players are separate."