Chelsea will return with a third bid for Rooney following Monday night's Barclays Premier League meeting between the sides, despite being told the striker is not for sale.
It was put to Mourinho that he will not be the most popular man at Old Trafford in a match where there is an opportunity to strike an early blow in the title race.
The self-proclaimed Special One said: "Why? They are against me?
"But I didn't say (to Rooney) you will be a second choice for me. And they are against me?
"We are trying to get a player that the manager told 'you will be a second option'. We are not going for (Robin) van Persie.
"They don't have to be against me. If I say Ramires is a second option for me and he plays when (Frank) Lampard is tired or injured, if somebody comes here to get Ramires, nobody is upset."
Asked if it is Moyes who is culpable for the Rooney situation, Mourinho said: "Of course."
Mourinho was referring to comments on Manchester United's pre-season tour, when Moyes, whether intentionally or not, suggested Rooney was a secondary option to Van Persie, remarks which led to claims the England striker was unhappy.
Mourinho added: "In every big team - (and) I am not criticising - you have first options and second options, and the second options, they must be very good players.
"That's why we are buying another good player (Willian) who will be in the same area of (Juan) Mata and Oscar and (Eden) Hazard and so on.
"Of course big teams must have second choices. Big players too.
"The point is if the players are happy to accept that situation or the players are not happy.
"A big club manager, of course we want to keep players in the squad because during the season we're going to need them."
Mourinho admitted he did not see much of Rooney while he was managing in Spain, but it is his belief that Rooney's secondary status - whether that is the reality or not - is down to the strength of United's squad.
"It means they have a fantastic squad," Mourinho added.
"I was playing against them last year. He was on the bench and he (Sir Alex Ferguson, then United boss) was playing Van Persie, Welbeck, (Shinji) Kagawa. The squad is amazing.
"So it is natural that some players have to be second choice. They have a fantastic squad."
Some say the pursuit of Rooney is a win, win situation for Mourinho and Chelsea - United are destabilised if he stays and weakened if he leaves.
Mourinho added: "If, in this moment, we want to upset them as some people were saying, now we'd be making a bid for the player every day - before the match.
"Now we are quiet, we have no contact. Nothing, nothing at all. (On) Tuesday, we will have another feeling.
"Our objective is to try to get a player who we think is a good addition for us. Nothing else."
Mourinho thinks it is odd that English clubs opt not to sell to each other.
"Most of the time in Italy it is about changing players in between clubs and making deals together - 'I don't need a striker, I have four, you don't have a midfield player, I have too much'," Mourinho added.
"It is something basic. The clubs don't spend so much money on these deals.
"It is good for the numbers, it is good for the players and it is good for the clubs."
It is clear Mourinho is enjoying his return to England after finding life in Madrid testing.
Asked by one Spanish reporter if he would answer a question in Spanish, Mourinho said: "I don't speak Spanish any more. I forgot."
Mourinho was long spoken of as a possible successor to Ferguson, whose retirement prompted Moyes' appointment.
One journalist asked Mourinho about joining the biggest club in the world, referring to United.
Mourinho's response was blue.
"Chelsea," he said, instantly, before singing "Chelsea, Chelsea."