Jose Mourinho branded Chelsea's display in their Champions League defeat at Real Betis as the worst performance by the Blues since he arrived at the club.
Betis' 1-0 win leaves the group wide open and means they are still a threat to Chelsea and Liverpool.
Mourinho said: "I've been here for 15 months and we have played perhaps 80 games at Chelsea and this was the worst performance. I cannot find a positive.
"The first half was too bad to be true. I know everything was bad."
Dani scored the only goal of the game after 28 minutes and the win means Betis climbed to within a point of the Londoners in Group G.
Mourinho admitted: "We have no defence or argument for it.
"We are a great team, but we were not a great team here. We have got to get back to our standards.
"There was a reaction in the second half and we almost scored when Michael Essien's shot hit both posts. We were not lucky and that was an almost impossible incident.
"But Betis deserved the victory because of their attitude in the first half and the way they defended in the second half.
"We have to look to ourselves to work out what didn't work and try to solve it."