Graham Potter's reign as Chelsea manager began with a 1-1 draw against Red Bull Salzburg at Stamford Bridge on Wednesday.
The result leaves Chelsea with an uphill task of qualifying for the Champions League knockout stages.
They have two points from two games and face two consecutive games against AC Milan, who top the group with four points.
Former Brighton boss Potter picked Raheem Sterling as an advanced wing-back and the gamble paid off when the forward curled into the bottom corner shortly after the break.
Chelsea produced a far better performance from last week's loss to Dinamo Zagreb, which was Thomas Tuchel's last game in charge.
But the home side were caught on with 15 minutes remaining when Thiago Silva missed a tackle, allowing Noah Okafor to clip in Junior Adamu's low cross.
Reece James and Hakim Ziyech both had late chances to win the game. Speaking after the game, Potter insisted his side would improve.
He told BT Sport: "We're disappointed with the result. I thought the boys gave everything. We scored a good goal, but lost a bit in the second half but their goalkeeper has made some good saves.
"It is what it is, we have to dust ourselves down. Personality and application was good, we will get better. We got Raheem in one-on-one situations quite often and the goal was a good result of that.
"It's always irritating when you concede a goal. Overall the defensive performance was quite good, it's just the little details we will have to improve.
"It has not been easy for the boys, they have responded to us really well over the last few days and it's a point we will have to take and get better. The attitude has been fantastic, no complaints apart from the fact we have not taken three points."