Chelsea interim manager Calum McFarlane lamented his side's poor start during Monday's 3–1 Premier League home defeat to Nottingham Forest, marking the London club's sixth successive league defeat.
Taiwo Awoniyi scored for Forest inside two minutes and then Chelsea fell further behind to an Igor Jesus penalty in the 15th.
Awoniyi struck again at the start of the second half, with Joao Pedro’s stoppage-time goal proving only a consolation for the hosts.
"Ultimately, the first 15 minutes was not acceptable," McFarlane told reporters.
"The early goal was a bit of a sucker punch. We know that they like to cross to the back post. We know that the No 9 likes to peel to the back post. We should defend that moment better."
Ninth placed Chelsea sit 10 points behind fifth placed Aston Villa, extinguishing any lingering hope of a top-five finish that would guarantee Champions League football next season.
They will face fourth-placed Liverpool on Saturday.