He was not angry, but he was more than just disappointed. 

Romelu Lukaku had just helped Manchester United beat old club Chelsea, ending his wait for a goal against major opposition in the process, when he was asked if he felt criticism of his big-game mettle was unfair.

"I've been in the game for so long," said the striker, having scored his first goal for the club against a top-eight team in 13 attempts. "I started playing when I was 16. Year in, year out, people expect 20 goals from me. I've been doing it for 10 years straight so I think I've proved myself.

"You expect a bit more respect but it's the situation we're in. I don't listen to it [the criticism]. I just want to improve and show the people what I can do on the pitch."

Looking just at Lukaku's numbers from this season, respect is the least he deserves. He has netted 23 goals in all competitions, setting up a further seven. Eight of those goals, including the strike in the 2-1 win over Chelsea, have come in his last 11 appearances.

He has scored as many as Luis Suarez, more than Gonzalo Higuain, Mauro Icardi, Kylian Mbappe, Alvaro Morata, or new Manchester United signing Alexis Sanchez in 2017-18. If he strikes against Liverpool on Saturday, it will be his 100th in the Premier League, at the age of 24.

As first seasons at a new club go, his has been excellent. And yet, the towering Belgian has been belittled at almost every turn. His run of 11 goals in his first 10 games following his move from Everton seemed to come with an asterisk: they were against teams United should regard as whipping-boys, it was said. 

As soon as he hit a barren run of one Premier League goal in nine outings, which included meetings with Liverpool, Tottenham, Chelsea, Arsenal and Manchester City, plenty were left chuckling at this £75million flat-track bully.

Of course, that is exactly one of the reasons United bought him. They drew league games with West Ham, Bournemouth, West Brom, Everton and Swansea City last season. Lukaku has scored against all of them in a United shirt, and all but one ended in a win. That is an extra eight points from those games alone in 2017-18.

Secondly, as Jose Mourinho has barked at critics at every opportunity, there is much more to Lukaku's role than the admittedly quite important task of putting the ball in the net. His hold-up play has improved markedly in his first eight months at Old Trafford. He also sets the tone when United are asked to press high, far more than Zlatan Ibrahimovic ever did as first-choice number nine last year. His sprints (he made 36 against Chelsea, and 54 in the comeback win at Crystal Palace) are essential to destabilise defences and give the likes of Sanchez and Anthony Martial room to manoeuvre, as well as prevent opposing defenders from bringing the ball forward.

He works tirelessly, both to get on the scoresheet himself and stop the opposition from doing the same. These are qualities Mourinho prides in his centre-forwards in equal measure: the moment the manager chose to roar to the Old Trafford crowd and whip them into a fervour against Chelsea was not after either of United's goals, but when, in the 93rd minute, Lukaku had won the ball on halfway, powered past three players into the champions' penalty area and earned a throw-in.

"He played fantastically well," said Mourinho. "At first he didn't find the right timing and lost the ball at times. But then he went together with the team and finished the game and people go home with the image of the run where he could have gone and got a goal."

Mourinho's United are still a befuddling entity. They are better than they were a year ago but still unable to string positive performances together on a regular basis, even if the results are decent. They are also having to cope with the unstoppable force casting its shadow across the city from the Etihad Stadium. It means there is always criticism to be found and, rightly or wrongly, it tends to gather around the players with the biggest price tags, as though wage packets and Instagram followers are magnets for the disdain of the football purists. 

In Lukaku's case, though, it is largely unfair. He can prove as much against Liverpool. A goal against Jurgen Klopp's side will not necessarily earn adulation, but it should get him some of that respect he craves.

Mourinho, of course, will not be concerned if he scores or not, as long as he helps claim victory. Since Lukaku was never on the winning side in a Merseyside derby, perhaps that will be enough for him, too. Perhaps it should be for everyone else.