Mourinho was angered by questions surrounding the absence of Belgian attacking midfielder Kevin De Bruyne, who did not travel to the Romanian capital after being left out of the squad.
The Portuguese's decision to leave Spanish playmaker Juan Mata out of a number of games this term has come under much scrutiny, although the 25-year-old is in line to start on Tuesday after setting up the equaliser in Chelsea's 1-1 draw with Tottenham last Saturday.
|15/4||Steaua Bucharest are 15/4 with BetVictor to beat Chelsea on Tuesday
"This is fantastic because no one asks me about [Juan] Mata. You have spoken about Mata for three weeks. Now you're asking about Kevin," he said.
"You are interested in the players who are not playing. He was not selected. It was my decision. Only 11 can play and I tried to decide, by what they do on the pitch when they play and in training.
"I try to be honest all the time. I was honest with Juan because of what he's done in training and what he's done in the game he played, and so he plays.
"With Kevin I didn't like the match he played against Swindon [in the League Cup], and I didn't like the way he was training.
"But you only ask about the guys who were not selected. Thank you."
Mourinho then left the room and will hope his players do the talking for him at the Arena Nationala as they look to bounce back from a 2-1 defeat to Basel in their opening Champions League fixture.