- With three games left for each team, group leaders Salzburg are one point above Chelsea after beating Dinamo Zagreb 1-0 on Wednesday.
Chelsea climbed back into contention for a place in the Champions League last 16 with an impressive 3-0 victory against AC Milan on Wednesday.
Graham Potter's side won for the first time in three Group E games as Wesley Fofana's first Chelsea goal was followed by second-half strikes from Pierre-Emerick Aubameyang and Reece James at Stamford Bridge.
Chelsea had kicked off their Champions League campaign with an embarrassing defeat at Dinamo Zagreb the day before Thomas Tuchel was sacked, while Potter's first match ended in a draw with Salzburg.
But second-placed Chelsea are now level with third-placed Milan on four points ahead of a crucial trip to the San Siro to face the Italian champions again on October 11.
With three games left for each team, group leaders Salzburg are one point above Chelsea after beating Dinamo Zagreb 1-0 on Wednesday.
Progress in the Champions League is essential to Potter's bid to stamp his authority on a squad expensively assembled by Chelsea's new owners with immediate success in mind.
While Chelsea still have work to do to reach the knockout stage, Potter will be encouraged by the most dynamic performance of his three games since replacing Tuchel.
The former Brighton boss has kept a low profile so far as he gets acclimatised to the first high-pressure job of his managerial career.
Potter had never attended a Champions League game before taking charge at Chelsea, so his first victory in the competition was a memorable milestone for the modest coach.
Fittingly, it was achieved with minimum fuss as Chelsea set the tone from the moment Mason Mount's curling effort forced a sprawling save from Ciprian Tatarusanu.
If that was an aesthetically pleasing way to take the game to Milan, the Blues wrestled control with a more rudimentary aerial assault that left Milan battered and bruised.
Exposing Milan's weakness at set-pieces, Thiago Silva met Mount's free-kick with a header that Tatarusanu tipped over.
Moments later, Silva threatened again with another header that deflected wide for the corner that produced Chelsea's 24th-minute opener.
- Knockout blow -
With Milan negligent in their marking yet again, Silva reached Ben Chilwell's corner with a thumping header that was parried by Tatarusanu.
Ruben Loftus-Cheek scrambled the rebound towards Fofana and the French defender fired low into the far corner from six yards.
Fofana's memorable evening turned sour following a challenge with Rafael Leao that forced the centre-back to limp off late in the first half.
Despite being outplayed for most of the half, Milan would have been level in stoppage-time if not for a woeful piece of finishing.
Leao scythed through the Chelsea defence to set up Charles De Ketelaere for a shot that Kepa Arrizabalaga pushed out to Rade Krunic, who blazed high over the bar from close range.
That narrow escape served to refocus Chelsea in the second half and they delivered the knockout blow in the 56th minute.
Former Chelsea defender Fikayo Tomori was caught out by James' cross and Aubameyang was on hand to volley home.
It was Aubameyang's second goal in successive games after the Gabon striker bagged his first for the club in their win at Crystal Palace on Saturday.
Aubameyang had endured a much longer wait to score in the Champions League -- this was his first goal in the competition since he netted for Borussia Dortmund in 2017.
Toothless in attack with former Chelsea striker Olivier Giroud anonymous and far too careless at the back, Milan were in disarray and it was no surprise when Chelsea struck again six minutes later.
Raheem Sterling fed the unmarked James with a perfectly-weighted pass into the Milan area and the defender slammed a fierce strike past Tatarusanu from a tight angle.