Jose Mourinho has denied "humiliating" Nemanja Matic by substituting him 27 minutes after he was brought off the bench in Chelsea's 3-1 defeat at home to Southampton.
Matic was brought on as a half-time replacement for Ramires, who had been booked shortly before Saints midfielder Steven Davis made it 1-1 in the 43rd minute.
However, Matic's introduction did not have the desired effect and he was taken off after Graziano Pelle had made it 3-1 to the visitors.
There were boos around Stamford Bridge as the supporters appeared to question Mourinho's decision to take off the midfielder, but the Chelsea boss said he felt he had no option due to the Serbia international's poor form.
"It was not humiliating -- I don't do that to anyone in football or life," he told reporters. "If I do, I do without any intention.
"I like them [my players], I trust them and I know they are good players but some of them are in a difficult moment and Matic is one of them. He's not playing well, is not sharp defensively and is making mistakes with the ball.
"I was afraid of Ramires being sent off. I kept Oscar because he creates more.
"I kept [Cesc] Fabregas because he is the one -- maybe because of his formation in a difficult place to play which is Barcelona -- who copes better with the pressure. His emotional stability is high.
"So I decided to take off Matic but I like the player very much, I have a fantastic relationship with the boy. Humiliating him? For sure, I was not."
Fabregas is also enduring a poor run of form, but Mourinho said the Spain international was still trying to play creative football.
"You feel the pressure," he said. "Some players are different than others and have a bigger personality.
"You can be critical of Fabregas because he is not playing especially well, I know that, but he never loses the confidence to try things, which for me is fundamental.
"I prefer a player that is not playing well but has confidence to try and is not influenced by the pressure or by some reaction from the crowd. I need the strong personality."
Mourinho -- who said last week he would field his youth players if Chelsea were to drop out of contention for silverware -- indicated that he is ready to give 19-year-old midfielder Ruben Loftus-Cheek a chance to impress in the upcoming game against Aston Villa on Oct. 17.
Mourinho had been under pressure to restore captain John Terry to the side after the midweek defeat at Porto, but the 34-year-old's reintroduction to the starting lineup brought little improvement against Southampton and the Chelsea boss said youngsters may be less affected by the current pressure.
The Portuguese said: "My job is not so simple because I have to measure the situation and it is to keep more experienced players with the pressure of the moment.
"When I don't play Terry and play [Kurt] Zouma, you [the media] say, 'Why don't you play John?'
"With Ruben, it's the same thing. It's about who can cope better with the pressure. Maybe a young player feels less pressure when the team is losing. It's time not to play four, five or six kids. He is more ready and if everything goes normal, he will start the next game and have a run of matches.
"I have to persuade him [though] not to feel the pressure."
Mourinho -- who has claimed his team have been unfairly treated by officials this season -- said his team is "very fragile" and crumbles like a "castle of cards."
He told Chelsea TV: "The team emotionally is very fragile. The team is feeling too much the pressure of the bad results, the negativity, the fact every time you make a mistake you are normally punished.
"When we make individual mistakes the team is like a castle of cards that collapses, because mentally the team is in trouble. The confidence levels are very low and the team is feeling that a lot.''
The former Inter Milan and Real Madrid boss said he wished he could play for Chelsea himself and admitted he is uncertain about the reasons behind the team's downward slide.
He added: "I'm so sorry that I don't have a game tomorrow. I'm so sorry that I am too old to play and I have no quality to play in a team like Chelsea.
"I am so, so sorry because I would love to play. I don't know what is good or bad for them in this moment."
Information from the Press Association was used in this report.