Milan were severely hindered by a man disadvantage after Fikayo Tomori was sent off early as he gave away a penalty, which Chelsea capitalised on with Jorginho converting from the spot. Soon after, Pierre-Emerick Aubameyang continued his good form by doubling Chelsea's lead to earn his side's fourth consecutive victory and continue their unbeaten start under Potter's stewardship.
"To come here and win is not easy," Potter told BT Sport. "Credit to the players. They were really good.
"We had a bit of luck with the opposition going down to 10 men. It's nice for the penalty and nice for Jorginho to score. It was a nice move to lead to it. It is what it is. Sometimes they go for you. Overall the performance was good. "
Chelsea won the reverse fixture 3-0 last week, and this edition sprung into action as Milan went down to 10 men just 18 minutes in. Tomori pulled on compatriot Mason Mount as the Chelsea midfielder burst into the box and, despite Mount not going to ground, Daniel Siebert awarded Chelsea a penalty, which Jorginho converted after three minutes of Milan protests.
"The penalty and red card changed everything," Milan coach Stefano Pioli told Mediaset. "Chelsea didn't need to play with a numerical superiority.
"I don't want to review the episode, it seems too obvious. I don't want to comment. I told the referee what I think, I don't speak English very well but I think he understood."
Chelsea asserted dominance with their man advantage and struck again in the 34th minute through Aubameyang.
The striker -- who has now scored three goals in his last three matches -- exchanged passes with Mount before firing an assured, side-footed finish past Ciprian Tatarusanu.
Chelsea did suffer a blow in the second half as Reece James was forced off injured just after the hour mark. James, who has been a peripheral figure for Chelsea this season, went down for a second time and had to be replaced, causing further injury worry for England ahead of the World Cup next month.
"Reece, we're hoping he'll be ok," said Chelsea manager Graham Potter after the match. "[We'll need] 24-48 hours because it's too early to tell you anything more than that."
Milan's home support rallied their side on to no avail as Chelsea's 11 men stood firm. Potter's side continued to forge openings but couldn't find a finishing touch in an ultimately comfortable night in Italy's fashion capital.