Carvalho said: "I don't understand why I've been told to wait for another chance to play this season.
"I don't believe I will be third choice. It's incomprehensible.
"I want to know why I didn't play. How can I explain it when I don't understand it?
"Sincerely I gave a lot of thought and time to myself but cannot find a valid explanation.
"I don't understand the reason he (Mourinho) put me in a group including Robert Huth, Joe Cole and Tiago.
"At FC Porto I didn't have an easy life with Mourinho, especially in the year he arrived," he said.
"But in time I recovered my confidence and finished in a big way. I don't want an identical situation at Chelsea."