Graham Potter admitted Chelsea must improve "little details" after Red Bull Salzburg spoiled his first match in charge with a late equalizer for a 1-1 draw.
Potter was on course for a winning debut when Raheem Sterling put Chelsea ahead early in the second half at Stamford Bridge.
But the former Brighton boss, who replaced Thomas Tuchel last week, saw Noah Okafor punish sloppy defending to equalize late on.
It was a largely underwhelming performance from Chelsea, pointing to the work Potter must do to repair flaws in Tuchel's expensively assembled squad.
"Overall the defensive performance was quite good," Potter said. "It's just the little details we'll have to improve."
Tuchel was dismissed last Wednesday after Chelsea's embarrassing 1-0 loss at Dinamo Zagreb in a Champions League Group E opener.
Having taken just one point from their first two group-stage matches, Chelsea now face a fight to qualify for the knockout stages with two matches against AC Milan looming.
"It is what it is," Potter remarked. "We will get better."
With Sunday's Premier League game against Liverpool postponed due to the royal funeral, Potter has to wait until October 1 for his second game when Chelsea travel to Crystal Palace after the international break.
At least that gives Potter time to find his feet. For he was appointed 24 hours after Tuchel went, setting off what the 47-year-old described as a "whirlwind" week.
