Erling Haaland made the difference in Portugal as his two goals secured a 2-0 victory for Manchester City over FC Porto in Enzo Maresca’s first Champions League game since taking over as manager.In a raucous atmosphere at a rainy Estadio do Dragao, City were immediately on the front foot and dominated the ball, even if Porto’s defence prevented them from creating clear-cut chances in the early exchanges.However, Maresca’s side grew in confidence and were only denied by some outstanding goalkeeping from Diogo Costa, twice denying Haaland with strong saves.There was a long pause in play before the break as Gabri Veiga required treatment after being caught in the head by Marc Guehi’s arm, with the City defender going unpunished despite the home side’s protests.Haaland finally broke through Porto’s resistance after half-time. Phil Foden did well to save a ball from going out of play, finding Enzo Fernandez, who picked out Haaland in the box. The Norway striker leapt and while he could not meet it with power, he guided it expertly inside the post.Porto had their chances to equalise in an open and exciting game. They were denied a penalty by an offside call, William Gomes almost scored after charging down Gianluigi Donnarumma, and Pepe mishit a volley when clear at the far post.But it was Haaland who had the final word, side-footing the ball into the net in the final moments after being picked out by substitute Rayan Ait-Nouri – his 59th goal in 59 appearances in the Champions League.In a chaotic finale Haaland was booked for grappling with Pablo Rosario (who was also cautioned) and Costa denied Fernandez with a superb save.Thom Harris and Sam Lee dissect the action…How did City get the best out of Haaland?After City’s 1-0 win over Coventry on the weekend, Maresca made it clear to debutant Iliman Ndiaye that he likes his wingers to stay high and wide. “He was dropping a lot, and we don’t need that. That space was more for (Josko) Gvardiol, we need him a little higher.”This evening, it was Semenyo who started out on the left. And though the 26-year-old was sometimes a little overzealous and loose in possession, he played the touchline-winger role much more to the manager’s preference, dragging defenders out wide and opening the space for the underlapping run. As we can see from the pass network below, Semenyo was often isolated out left, but enjoyed the support of the forward run from Fernandez or Gvardiol when it came.When that happened, Semenyo was afforded space to cut inside and curl crosses in with his right foot. That brought Haaland into play, consistently found with floated crosses towards the striker’s towering frame, eventually breaking the deadlock with a familiar looping header back across goal.That came after an underlapping run from Rayan Cherki, while City’s best chance in the first half came as Phil Foden stormed through the inside channel and received from Semenyo, standing up the cross to the back post.Haaland’s second — rolling the ball into the bottom corner with his right boot — brought a streak of three headed goals in succession to an end. That is no coincidence, given a very rehearsed sequence of movements down the flank from the Maresca playbook.Thom HarrisShould Marc Guehi have been sent off?City’s control of possession and territory throughout the first half largely pacified Porto, but intensity simmered below the surface. Relentless right winger Gomes pressed Gvardiol hard whenever he received the ball, a recurring battle that eventually drew a card for the City defender and led to a flare up in the tunnel at half time.Those tempers were not helped by the nasty collision between Guehi and Veiga just before the break, as the Englishman clattered into the midfielder in attempt to head the ball away. It happened quickly — Guehi attacked the ball at full speed and caught his opponent in the face, leading with his right arm and causing Veiga a black eye. Guehi was given the benefit of the doubt as he used that arm for leverage. It looked worse and more intentional when slowed down — Guehi’s elbow far from his body as he jumps — but in real time you have to assume that this was an unfortunate clash. That won’t have made it any less painful.Aside from that moment of clumsiness, Guehi was arguably City’s most composed defender on the night, making a series of important interventions and progressing the ball well down the left.Thom HarrisHow did Ayyoub Bouaddi perform on full debut?Ayyoub Bouaddi was replaced by Mateo Kovacic after 75 minutes but it could not have been due to a poor performance, after the 18-year-old Morocco international looked impressive on his full City debut.European football may suit him better as he gets to grips with City and the Premier League, but in truth it is still some feat for such a young player to look comfortable at this level. City had to fight for their win and Bouaddi was involved in everything, whether taking the ball under extreme pressing and finding a team-mate, or getting his foot in to break up attacks.Ayyoub Bouaddi looked assured in possession (Miguel RIOPA / AFP via Getty Images)He is clearly already trusted by his team-mates to take the ball in those tight areas, seemingly especially by Rayan Cherki, who had no qualms giving him a ‘dirty’ ball and expecting it to come out clean. City knew they were signing a player with a very high ceiling, but they also have a player who can make big contributions right now. Other players were withdrawn by Maresca after struggling in the game, but that cannot be said for Bouaddi.Sam LeeWhy did Maresca take off Cherki and Semenyo?Maresca was indeed decisive with his changes at the Dragao. Gvardiol looked jittery early on, rallied a little to break up some dangerous Porto attacks, but then started giving the ball away again and was booked for a needless pull after being caught dawdling in possession.The home fans wanted a second yellow just before the break and although there was never much in it, it had marked his card, and so it was perhaps no surprise that he was soon withdrawn — only that it came immediately after the 47th-minute goal, rather than at the break.That hints at another issue but Maresca was not messing around when the game started to get stretched midway through the second half, taking off Cherki, who had started to lose the ball when City had the chance to score a second, and Semenyo, whose poor touches often thwarted his side’s attacks.Elliot Anderson and Ndiaye helped City to keep a lid on things. Bouaddi and Foden had fared much better before they were substituted with 15 minutes to go, hinting at fatigue or a desire from Maresca to get some fresher legs on.After City’s ultimately impressive transfer window, they do have the option to do that.Sam LeeWhat did Maresca say?We will bring you this after he has spoken at the post-match press conference.What next for City?Sunday, September 13: Manchester United (Away), Premier League, 4.30pm BST, 11.30am ET