When required Manchester City moved into a high gear, pulling away from Porto as the second half wore on. For that Pep Guardiola deserves credit for a double substitution that introduced Phil Foden and Ferran Torres, the pair soon combining for the latter’s goal that made the points safe. It meant City began their campaign in fine fashion and in a Group C also featuring Olympiakos and Marseille they will surely be hard to stop. Yet in a schedule that is particularly hectic the sight of Fernandinho, himself a replacement, limping off near the final whistle was unwelcome. The veteran joins Kevin De Bruyne, Aymeric Laporte and Gabriel Jesus as senior players who are currently unavailable. Guardiola said: “He has a muscular problem in the place where he was injured. [At a guess] he will be out four to six weeks – we need people but it’s what it is. On Thursday we’ll start with Kevin and Laporte training again but I don’t know how they’ll come back. We get players back and others we lose, in three days we go to London [to play West Ham] and then to France to play Marseilles [Tuesday] and then Sheffield [Saturday]: it’s so demanding.” Of Wednesday’s win the head coach said: “It was a perfect performance against a very good team.” Porto arrived as Portuguese champions for a 29th time, and 14 minutes in Rúben Dias’s impressive start to his City career faltered. The £64.3m signing looked at ease in his opening two matches but here he contrived to pass straight to Mateus Uribe. He fed Luis Díaz and City’s whole rearguard fell apart. The No 7 was allowed to run across the field from the left, pass a static Rodrigo, then João Cancelo who shied away, before beating Ederson with a powerful angled shot. This was a calamity for City but they responded instantly. Suddenly Ilkay Gündogan smacked a shot off Agustín Marchesín’s right post and Pepe was clattering Raheem Sterling, sending him to the ground. Andris Treimanis awarded the penalty, VAR vindicated the referee, and Sergio Agüero beat Marchesín, the ball going in off the goalkeeper’s body to his right. But City again showed a penchant for self-harm. Trying to play out from the back, Ederson hit the ball straight to Uribe and was left stranded: Uribe should have scored but to Sérgio Conceição’s obvious chagrin, the chance was spurned. There was further flaky defending when Zaidu Sanusi skated along the left and made Ederson save from a low angle. Then, a slumbering Eric García allowed Moussa Marega to slide in behind and City were scrambling to clear, García finally hoofing away. By the break Kyle Walker, Bernardo Silva and Cancelo had all been booked: a clear sign of how Porto were disrupting their opponents, though Treimanis was a little trigger-happy with the cards. For the second half Guardiola rejigged tactically, switching to a 4‑3‑3, Agüero splitting Riyad Mahrez and Sterling to his right and left, Rodrigo doing the same with Silva and Gündogan. A combination from the latter two had Gündogan volleying a shot that had Guardiola raising his arms to celebrate only for Marchesín to save superbly to his left. This was followed by a bright João Cancelo run that took the left-back along his flank but his cross did not threaten. But then, the previously composed Walker committed an error that allowed Díaz to move in at Dias, only for Rodrigo to see and snuff out the danger. At this point the contest was open, in itself a minor victory for Porto. City were certainly not the sleek proposition that dismantles sides at will. A Gündogan free-kick found Rodrigo but his header was misdirected away from the waiting Sterling. And when Walker burned down the right flank his cross found Agüero but the centre-forward was penalised for handball. All this was indicative of how City could not quite click. But as the match aged they surely fancied themselves to do so as Porto’s attacking intent had faded. And, thus, Gündogan struck after Fábio Vieira fouled him. The midfielder picked himself up and curled the free-kick sweetly past Marchesín to give City the lead. It also allowed them to relax despite an ever more vocal contribution from Porto’s bench. Foden and Torres were on and when the former played the latter in on goal, the Spaniard gave Marchesín no chance. From here City pinged the ball around at will, with Pepe lucky to stay on the field following a skirmish with Sterling, Rodri also hitting the post from distance.