Chelsea’s Champions League campaign has its ignition point and so does the managerial tenure of Graham Potter. It feels strange to think that this was only his third match in charge of the club following his appointment on 8 September, the first having been the 1-1 draw here against Red Bull Salzburg. That had been a strange jumble of emotions in the wake of the loss at Dinamo Zagreb and Thomas Tuchel’s sacking. But with Chelsea desperately needing a victory in the competition everything came together, the blue shirts pouring forward from all angles; Milan chased out of west London, fortunate to escape a serious beating. It was still chastening. There is a particular kind of event glamour when it comes to Milan – the cool shirts; the sight of Paolo Maldini, the technical director, strolling the touchline before kick-off. Clarence Seedorf, the former Milan midfielder, was here as a media pundit – alongside the Chelsea icon, Gianfranco Zola, in front of the press box. But apart from the electricity generated whenever Rafael Leão got the ball and started to run, Milan offered nothing and it was certainly jarring to see the champions of Italy defend so generously. The die was cast when Wesley Fofana opening the scoring midway through the first half following a poorly defended corner and, thereafter, Chelsea threatened to run riot. Potter has had to feel his way into the role on the training ground and he could delight at how his players mapped the moves from Cobham on to the big stage. Pierre-Emerick Aubameyang added the second and it was a night when pretty much everybody impressed. Thiago Silva was pitch perfect in defence while Mateo Kovacic and Ruben Loftus-Cheek ran the midfield. But, as so often, it was Reece James who was the dominant figure. The right wing-back drove the team, a menace to Milan with his surges and deliveries. It was his cross that teed up Aubameyang and it was fitting that he set the seal on one of the best Chelsea victories for some time with the third goal, slammed high inside the near post after a Raheem Sterling pass. It was James who the TV cameras followed at full-time, him that the home crowd saluted in song. Chelsea had flickered at the outset against a Milan defence that missed the No 1 goalkeeper, Mike Maignan, and three of the regular back four – Davide Calabria, Simon Kjær and Theo Hernández. Mason Mount extended Ciprian Tatarusanu but it was after a flurry of set pieces midway through the first half that Chelsea took control – four of them to be precise, each bringing a free header and worry lines for Stefano Pioli, the Milan manager. How was this happening? From the fourth, a Ben Chilwell corner, Silva – as he had done twice previously – unloaded his header, which was pushed out by Tatarusanu and from there, it was a scramble. Aubameyang put himself about, so did Loftus-Cheek and, when the ball broke, it did so kindly for Fofana, who rolled it home. Chelsea were well balanced in Potter’s 3-4-2-1 system; Sterling and Mount finding spaces as the No 10s, James and Chilwell offering width and thrust. They might have been out of sight by the interval. Mount saw a shot blocked after James had combined with Sterling to pull back, and Mount also had the ball in the net after a nice finish but had strayed offside. Sterling, too, went close on a quick break. Milan’s threat came exclusively through Leão, their fast rising star – an uncommon blend of explosiveness and strength. His first involvement had been to blast away from a clutch of blue shirts and he made it clear that he intended to do it again and again. Chelsea needed Silva to stretch into an excellent slide challenge on him in the 19th minute after Fofana had been caught on the ball. What a run it was that Leão produced in first-half stoppage time, taking him past four Chelsea players, the alarm bells ringing loudly. Charles De Ketelaere prodded goalwards and, when Kepa Arrizabalaga – who kept his place ahead of the fit again Édouard Mendy – patted the ball out, Rade Krunic had to score. From point-blank range, his shot went high. It was a huge let-off for Chelsea. There was needle, some bad challenges, with those from Krunic and Fodé Ballo-Touré in the first half fully meriting their yellow cards. But there did not appear to have been much in the tussle between Fofana and Leão that saw the former forced off on 38 minutes. The frustration for the goalscorer was intense. Chelsea deserved a second goal to allow themselves to breathe more easily and it came on 56 minutes when James crossed and Aubameyang gave Fikayo Tomori the slip all too easily. Tomori was left to perform a despairing lunge; it was a horror moment for the Chelsea youth product. That was that in terms of the result. But after Sterling had volleyed high, James brought the flourish.