The 24-year-old endured another frustrating afternoon on Saturday when United's eked out a 1-0 win against promoted Brighton as Ashley Young's strike looped in off Lewis Dunk.
Lukaku has mustered just one goal in his past 10 matches for United following an impressive start to life at Old Trafford but Mourinho refuses to criticise the striker.
"In the last minute he was fighting and running back like he was in the first minute, so I think it is also a mentality question," Mourinho said of Lukaku. "The way Romelu wins the corner for the goal, the way Romelu ends the game making tackles in the left-back position, that is the mentality I want. And, unfortunately, not every player is the same. Players are men, men are different. Men are unique cases.”
Mourinho added Lukaku showing hunger for the ball is enough for him as a manager. "Some guys are capable to go into the limits of their efforts and some other guys even with a lot of talent, they don't manage to do that. So Romelu, for me, fantastic. Didn't score, I don't care,” he said.
Mourinho has publicly questioned the mentality of some players during his time at United, but his frustrations have not been restricted to players.
The Portuguese has recently taken United fans to task, unhappy with their support of Lukaku against Tottenham and some general impatience in the stands.
"Honestly, it is quite a surprise for me but I think the supporters were fantastic," Mourinho said after the Brighton game. "We had matches at home where we played really, really well and they were a bit soft. And today they were behind the team. The team was not playing well, the team was 0-0, they support the team, they support the players."
However, with goals having dried up for Manchester United in their recent matches, Mourinho will hope to find the right attacking formula at high-flying Watford on Tuesday.
Mourinho said he had played with "too many attackers" against Brighton after aligning Anthony Martial, Marcus Rashford and Juan Mata behind Romelu Lukaku and now seems likely to change tack.
"(Against Brighton) our creation was poor," he said. "The three players that played with Lukaku did not get the ball. We weren't successful on the one-against-one. Marcus did not have a happy match at all. So we did not have that creation and could expect some defensive problems against a good team on the counter-attack."
With the Manchester derby at Old Trafford looming on December 10, Mourinho says he will be happy to pick up points however they are obtained.
"In the Champions League (against Basel), we played some of the best football away from home in the first half and could have been 6-0, but it was 0-0," he said.
"I am not happy with that, but (against Brighton) we scored one and one goal was enough for the three points. Because in the end we speak about what we want, but the points is the most important."
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ