Graham Potter admitted Chelsea were punished for their shoddy defending in the 2-2 draw with Everton.
Ellis Simms’ last-minute equaliser at Stamford Bridge denied Potter’s side a fourth straight win.
“We’re really disappointed because we’ve dropped points at home,” said the Blues boss.
“There were a lot of positive things in the performance but ultimately we haven’t defended well enough.”
After Joao Felix had put Chelsea ahead, Abdoulaye Doucoure scrambled the ball in to haul Everton level.
Kai Havertz’s penalty restored the hosts’ lead but they were caught out by a late counter-attack.
Potter said: “The first goal is really disappointing from a set-piece perspective and then for the second goal we haven’t attacked well enough and then exposed ourselves to a big space to defend and haven’t done it well enough.
“These little things, when you look at how much we put into the game and how much we tried to attack, to be cheap with the goals we conceded is frustrating.”