The away side took the lead through Diaz early on in the first half, but Manchester City came back into the game through Sergio Aguero’s penalty on the 20th minute.
The Premier League side did well to take the lead around the hour mark through Ilkay Gundogan, and Ferran Torres wrapped up the scoring a few minutes later.
Pep Guardiola will be reasonably pleased with his team’s performance in the opening group game of the Champions League today, and Manchester City will be looking to build on this and improve in their upcoming matches.
The Spanish manager has failed to win the Champions League during his four seasons at the club, and he will be hoping to guide the Premier League side to a Champions League win this year.
Manchester City certainly have the quality to go all the way in the competition, but they will have to address their inconsistencies.
They were firm favourites heading into the game today, and the fans will be pleased with the outcome.
It will be interesting to see how Porto react to this defeat in their next game.
The Portuguese outfit will fancy their chances of getting out of the group, but they will have to improve a lot in the upcoming matches in order to do so.