Pep Guardiola called Manchester City’s 3-1 victory over Porto a “perfect performance” after his side came from behind to open their Champions League Group C campaign with three points.

City were made to work hard after Luis Diaz capitalised on a loose pass from Ruben Dias to put Porto ahead after 14 minutes.

But a Sergio Aguero penalty drew City level before the break, and goals from Ilkay Gundogan and substitute Ferran Torres – the latter on his Champions League debut – completed the turnaround.

“We knew how tough it would be because Porto and Benfica are the best teams in Portugal,” Guardiola said. “They have the winning mentality, they have to win every game.

It was one of several puzzling decisions from Andris Treimanis which drew the ire of the Porto coach.

“The refereeing was of high importance, and I don’t think we deserved such a weak team of officials,” Conceicao said.

“In terms of the game, clearly City had difficulties in the first half, not just in how we defended but also how we attacked.

“I think it was a game where we played well despite the refereeing. It was an unfair result in my opinion.”