RB Salzburg spoiled Graham Potter’s first match in charge of Chelsea by claiming a 1-1 draw at Stamford Bridge in the Champions League.
Raheem Sterling’s curled strike should have handed new boss Potter lift-off on his Champions League and Blues bow.
But a mistake from Thiago Silva opened the door for Noah Okafor to snatch a draw for Salzburg with a neat finish to cap a counter-attack.
Chelsea were back in action after the Premier League’s weekend hiatus due to the Queen’s death, but the Blues could not atone for last week’s 1-0 Champions League loss at Dinamo Zagreb.
Potter employed a clutch of formations in a shape-shifting Chelsea set-up, but 37-year-old Brazilian Silva always appeared under duress at the back of that system.
The defender conjured many a manful intervention only to slip just shy of completing a slide tackle – which allowed Salzburg to steal in and secure a leveller.
Chelsea’s one point from two matches left Potter’s men bottom of Group E, with AC Milan top on four points.
The Blues can still rectify their situation and reach the knockout stages, but will likely need to beat Milan home and away in their back-to-back matches with the Italians in October.
Chelsea sacked Thomas Tuchel last week with new owners Todd Boehly and Behdad Eghbali installing a new manager in Potter they believe will work in sync with their long-term visions and ideas.
The Blues suffered many of the same troubles that had dogged Tuchel’s Chelsea in recent weeks however, with lots of work ahead for the club.
Sterling slotted the first goal of the Potter era to open the second half, and also calm concerns after a patchy first 45 minutes.
Chelsea had looked fluid in set-up and comfortable on the ball in their first half under Potter, but still failed to gel in the final third.
Reece James rifled in a fine cross but after Pierre-Emerick Aubameyang could not reach the ball in the middle, Sterling failed to make anything happen on the inside left.
Benjamin Sesko actually mustered the only shot on target of a stodgy first half, the Salzburg striker forcing Kepa Arrizabalaga into a solid save.
Almost every time Chelsea sought a final pass, either the ball itself or the run were off kilter.
The interval settled the hosts however, and a compelling move yielded the breakthrough almost immediately.
James spun his man and raced down the right before setting Mason Mount free, and the England midfielder sent an early ball into the box.
When Salzburg missed the chance to clear, Sterling pounced on the loose ball at the far post, took a steadying touch and then curled sweetly into the far corner.
Mount had to produce a timely sliding block to cut out a Salzburg attack as the match meandered after Chelsea’s opener.
Mount’s vital intervention encapsulated a clear push back to form, in what must be regarded as his strongest showing of this new season.
Okafor went close with a flicked header as Salzburg continued to press, but Kepa was sharp enough to smother the deft effort.
Chelsea had dominated possession throughout but had always appeared shaky when losing the ball.
And that instability proved costly when Salzburg broke at pace and punished the hosts with Okafor’s equaliser.
The otherwise-flawless Silva was pressed into one recovery job too many, and an incomplete slide tackle allowed the visitors the opening they needed to find the net.
Okafor powered in front of the cover and slid a neat finish past Kepa to put the game back in the balance at 1-1.
Philipp Kohn produced a point-blank save from Hakim Ziyech to deny Chelsea after a smart break between Armando Broja and Sterling.