Chelsea enjoyed a comfortable victory at AC Milan after former Blues defender Fikayo Tomori received an early red card.
Tomori was sent off for pulling back Mason Mount in the area, with Jorginho converting the penalty.
Pierre-Emerick Aubameyang doubled the lead with a confident strike against his former club.
But Chelsea and England suffered a blow in the second half when right-back Reece James limped off.
The win continues Graham Potter's unbeaten start as Chelsea manager, with four wins in his first five games.
It moves Chelsea top of Group E with seven points from four matches, but it remains extremely tight with Red Bull Salzburg on six points and both Milan and Dinamo Zagreb on four.
Blues manager Graham Potter later said: "To come here and win is not easy. Credit to the players. They were really good. We had a bit of luck with the opposition going down to 10 men. Overall the performance was good. It's nice to keep a clean sheet and to come away with three points is fantastic."
On the red card, he added: "It's hard from where I'm sitting. It looks like he had his hand on him and Mason Mount was through on goal. I need to look again clearly. 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
"It's tricky. You want to control the game but not to be too passive. With the atmosphere here, one action can result in a goal, the stadium erupts and they feel like they have an extra man."
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