The Premier League champions currently sit 14th in the table after seven games, having just won twice in the league.
Chelsea, who kept 17 league clean sheets last season, have kept just one so far against Arsenal, and have conceded 14 goals. Only Sunderland, who are bottom, have let in more in the league.
No team have allowed their opponents more shots on target than Chelsea, while Saturday’s opponents Southampton have allowed the fewest in the league this season.
“I define this as the worst period in my career. It’s a fantastic experience, even though I don’t want to repeat it again,” Mourinho told reporters at the club’s training ground at Cobham, south of London.
“Players know when they make mistakes. I don’t know what it’s like in your offices, but nobody seems to care about your mistakes,” he said.
Mourinho refused to be drawn on the subject of Eva Carneiro, the former first team doctor who quit after being criticised by the manager. Although he was cleared by the FA of discriminatory charges against the doctor, FA chairman Greg Dyke said on Thursday Mourinho was in the wrong and should have apologised.
“I’m not going to comment, one day I will but not today,” the 52-year-old said.
Branislav Ivanovic has been heavily criticised for his performances this season but Mourinho continued to back the player, saying the Serbia international was the best right-back in the league, but conceding that his form must improve.
“I have no doubt Ivanovic is the best right-back and also no doubt he needs to improve his form.
“He likes to speak with me about mistakes. He doesn’t cry about it like some newspapers,” he said.
“There is open communication between everyone here, with no crying and no prima donnas,” the former Real Madrid manager added.
Mourinho said he had no fresh injury worries after the 2-1 midweek Champions League loss to Porto.
Thibaut Courtois’s recovery from injury is going well, with the keeper expected back in December, the Portuguese said, while confirming that he was hoping to sign former Italy keeper Marco Amelia, who has been training with the team.
Apart from the poor results, the other issue troubling Chelsea’s fans has been the absence of club captain John Terry from the starting lineup.
Terry has been an unused substitute four times in the last five matches, with the Chelsea faithful chanting “we want our captain back” after their defeat at Porto in the Champions League on Tuesday.
Asked about Terry’s situation, Mourinho replied: “I am happy they sing and support John. It is more important they support John when he is not playing. He is ready to play every game, even when I leave him on the bench, he is ready to play.”