Maurizio Sarri insists Chelsea can still claim a Premier League top-four finish, but has warned it will be "impossible" unless his players improve.
Sarri admitted he is concerned by Chelsea's fragile mentality after their hopes of a Premier League top-four finish were dented by a 2-0 loss at Everton.
The Blues dominated possession and territory in the opening half at Goodison Park, and Eden Hazard saw a deflected strike come back off a post, but the visitors faded badly after the interval.
In contrast, Everton were rejuvenated and went ahead through Richarlison's header shortly after the resumption, while Gylfi Sigurdsson's scored on the rebound after his 72nd-minute penalty was saved.
Chelsea remain sixth in the table - three points behind fourth-placed Arsenal - and Sarri wants to see a big improvement from his players if they are to qualify for the Champions League next season.
Asked about Chelsea's top-four hopes, Sarri said: "It's not impossible, why impossible?
"We need to recover only three points so it's not impossible in eight matches.
"It's impossible if we are not able to improve, if we are not able to avoid a second half like today.
"We need only to play like in the first half for the next eight matches."
Sarri was at least enthused by what he witnessed in the first 45 minutes - even if he is mystified by the sudden drop-off in performance levels.
"We played probably the best 45 minutes of the season then suddenly, at the beginning of the second half, we stopped playing. I don't know why," he said.
"The situation is clear, it's impossible that the problem is a physical problem because if you have a physical problem, you can go down gradually, not in one second.
"We continued really very well until the last minute of the first half and (were playing) suddenly very badly in the first minute of the second half.
"It's very difficult for the players to explain to me the change and it's very difficult for me to explain to you the change. But probably it's a mental block, I think.
"I am worried about our mentality but we played the best 45 minutes of the season."
Additional reporting by the Press Association.
