José Mourinho has branded as unacceptable the form of a core of his title-winning team this season and warned he will make changes to his lineup if improvements are not immediate after Chelsea’s worst start to a domestic campaign in two decades.

The manager, who expressed dismay at suggestions some of his squad may be resting on their laurels from last term in the wake of Saturday’s home defeat to Crystal Palace, will now hope there is late progress in his club’s long-standing pursuit of the Juventus midfielder Paul Pogba before Tuesday’s transfer deadline. Any interest in the Tunisia centre-half Aymen Abdennour has been dropped after he swapped Monaco for Valencia, while Zenit St Petersburg will resist attempts to prise away the Argentina defender Ezequiel Garay.

Mourinho voiced frustration more progress had not been made to secure those pinpointed on his list of summer transfer targets, submitted to the board in late April, though his immediate task remains to reinvigorate members of his current squad. Asked whether his team retained the appetite to defend their title, the Portuguese said: “If that is the point, it is very, very sad because, for me, I feel the opposite. When I win, I want to win again. My medal is at home, in a drawer, [because] I feel fantastic motivation for more. If you win it once and the next [year] you are not on fire, not ready at least to fight for more, that is sad.

“City reacted to the fact they had lost the title by buying fantastic players. They are buying more until the end of the market. This is their job and, if they have the economic potential to do that, good. They did well. You see my players on the pitch and you could clearly identify two or three who can do better. It is not a question of loyalty: [my job] is to analyse if they are ready to give an answer and fight against that bad individual form.”

Asked specifically about Eden Hazard, the Footballer of the Year who endured another ineffective afternoon against Palace, he added: “If you are the best player in the Premier League it should be a good responsibility to have a similar season than in the previous season. I don’t want to analyse individual performances. In general terms, it is difficult to have a consistent performance when some of the players are not performing at a good level. When you have six or seven performing and three or four who are not an acceptable level, it is hard for a team to be consistent in the performance.

“I don’t know [why this is happening]. I don’t have an answer for everything. You have players who have fantastic seasons and fantastic moments and, the next season, do not have the same. I don’t want to speak about names from other teams, but I can perfectly tell you fantastic players who had bad years last season.

“Will I accept this, cross my arms, sit in a nice chair and wait calmly for the performance level to be back? No. I have to work, react, analyse and, if I feel the players are not in conditions to react and give more, I have to make changes. I have never had a problem with that.”