A decimated Milan made numerous mistakes in their heavy 3-0 Champions League defeat to Chelsea and above all barely threatened upfront.
The Rossoneri came in as group leaders, but missing 12 players through injuries and squad restrictions, doing without Theo Hernandez, Davide Calabria, Simon Kjaer, Mike Maignan, Alessandro Florenzi, Alexis Saelemaekers, Zlatan Ibrahimovic, Junior Messias, Yacine Adli, Malick Thiaw, Aster Vranckx and Tiemoue Bakayoko. Chelsea sacked Thomas Tuchel to bring in Graham Potter, but N’Golo Kante was injured, with Jorginho and Marc Cucurella only fit for the bench.
Milan dominated possession, but Chelsea created the early chances. Mason Mount forced the first low save from Ciprian Tatarusanu after a rapid counter, then Thiago Silva’s header was fingertipped over the bar from a free kick.
A series of Thiago Silva free headers were allowed on set plays in quick succession and eventually it paid off, as Tatarusanu parried and Wesley Fofana was quickest to turn in after a six-yard box scramble.
Mount had a shot charged down by Pierre Kalulu, then was flagged offside when lobbing Tatarusanu after a give-and-go.
Fofana went off with a knee sprain and a desperate Tomori block prevented Raheem Sterling going clear on goal.
Milan had a huge opportunity on the stroke of half-time, as Leao squirmed between four defenders in the box to set up Charles De Ketelaere, who forced a crucial one-handed save from Kepa Arrizabalaga, Rade Krunic firing the rebound over.
Chelsea scored another with more shaky defending, as Reece James whipped in a cross from the right that both Fode Ballo-Toure and Tomori failed to block, allowing Pierre-Emerick Aubameyang to tap in from six yards.
There was a third and again the young defenders were at fault, trying to play out from the back and getting caught out by James to blast into the near top corner from a tight angle.
Because RB Salzburg beat Dinamo Zagreb 1-0, it is an incredibly tight group with the Austrians on five points, Chelsea and Milan four, Dinamo three.
Chelsea 3-0 Milan
Fofana 24 (C), Aubameyang 56 (C), James 62 (C)