Belgium global Lukaku enjoyed a flying start to life at United, scoring 11 times in his first 10 appearances after joining from Everton for £75million ($129M).
The Portuguese was asked after Saturday's 1-0 home win over Tottenham if Pogba, who has been undergoing rehabilitation in the United States, had any chance of returning before the forthcoming worldwide break.
Lukaku will be hoping to rediscover his scoring form quickly as United are next in action against Benfica in the UEFA Champions League before making the trip to Stamford Bridge on Sunday to face reigning Premier League champions Chelsea.
"The fans are the fans and I am also told the fans pay for their tickets and they are free to express themselves the way they want to express themselves", Mourinho said at United's training base. Mourinho read something else into it, seeing it as mistreatment of Lukaku.
"I don't think he's quiet at all", he said.
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"I don't think it is fair at all".
"I think, like many people, that Romelu is a great forward".
Mourinho still has a strong squad to choose from tomorrow as he looks to secure a win over Benfica that would book their place in the knockout stages having already picked up maximum points from their three group games so far.
"The players felt it was quite easy to win against CSKA and Basel and they also felt it was hard to beat Benfica, it could have quite easily ended 0-0 or 1-1", he added. It was a hard match that could have been a draw between two big teams. So, I'm a bit disappointed - but not with him.
"I reviewed the game against CSKA [a 2-1 home defeat] and found it quite hard to understand how Benfica lost that match".