Chelsea manager Enzo Maresca was disappointed by how his side conceded two second-half goals to throw away their lead and slump to a 2-1 Champions League defeat at Atalanta on Tuesday.
Joao Pedro broke the deadlock for Chelsea after 25 minutes, but Serie A side Atalanta returned with far more intent after the break and overturned the deficit through goals from Gianluca Scamacca and Charles De Ketelaere.
Maresca said his side should have taken the chances they had to add to their first-half lead.
"After we conceded the 1-1 (goal), we lost a little bit of control of the game, and then we conceded the second one," he told reporters.
"I think both goals, we can avoid both of them. They're quite easy goals."
The win put Atalanta near the top of the Champions League table, putting them in the mix for direct qualification for the round of 16 with 13 points, while Chelsea have 10.
If the Premier League club do not win their remaining games against Cypriot side Pafos and Italy's Napoli, they will likely finish outside the top eight and be forced to play a two-legged playoff match.
"Probably with two wins, probably with 16 points, you can be in the top eight," the Italian manager added.
"Not sure about that, but now the focus has to be the next game. And then the next one, for sure. If we want to try to finish top eight, we need to win both.
"Otherwise, we try to play the playoff and then go to the next round."
Chelsea next host Everton in a league match on Saturday.