Lukaku wasn't the only impressive United debutant, with Nemanja Matic delivering a solid display that underlined why Chelsea manager Antonio Conte was so miffed his club sanctioned the £40 million sale of the Serbia midfielder to a title rival.
Despite being top of the league Mourinho insisted the early win means little in the context of the season.
"He wants more at football's highest level", said Mourinho.
Asked by MUTV if he could have hoped for more, Lukaku replied with a wry smile: "I wished to have three goals and a hat-trick to be fair, that would have been nicer".
The Premier League match between Manchester United and West Ham will be broadcast live online and on NBCSN.
The club made headlines when they signed Chicharito in the transfer window, and the biggest headline for this game will be the fact that United's favourite super-sub is likely to make a return to Old Trafford. They have two players for every position and that is why I am suggesting they will be the main title contenders alongside Manchester City.
"We are much better organised in the areas that support the first-team squad".
"Obviously were still missing a few players but that shows the strength of the squad - although we're missing some players we still have the quality to go there and do something good".
"So we are having conversations and we are discussing the possibility of him staying with us for the second part of the season". "It is a disastrous result for us and the worst scenario that could have happened". "I think the competition can be better than ever".
Manchester United is injury free expect long time absentees Luke Shaw, Marcos Rojo, and Ashley Young. To be in that stadium again, to play and to try to win with my new team is what is in my mind. Man City - fantastic boss, great spending, already very good players, they are equipped.
"When you come out on top it is an unbelievable feeling to know you are the best team in the country, and you have gone through all sorts of things along the way to win that".
"For us it's just another game, a game we look forward to - these are the kind of games players want to play", Fonte concluded.