Romelu Lukaku arrived at Manchester United this summer with a weight of expectation on his shoulders.

At just 24 years of age, the Belgian cost £75 million and was presented with the task of supplying the goals United would miss from last season's top scorer, Zlatan Ibrahimovic.

The Swede was released in the summer before signing a new one-year deal in August, following a long-term injury sustained in the Europa League in April, which will rule him out until the new year.

And that, on top of the fact that the club's all-time record goalscorer, Wayne Rooney, returned to boyhood club Everton had heightened the expectation on Lukaku.

But it appears that his huge move to Old Trafford has not phased him; with his seven Premier League goals currently putting him at the top of the scoring charts.

It's that kind of form in front of goal that could be the difference in the title race, with their cross-city rivals Manchester City currently only topping the league table on goal difference.

The striker has come a long way since the days he was an outcast at Chelsea, and shipped out on loan to West Brom and Everton, before making his move to the Toffees permanent.

And Belgium's coach, Roberto Martinez - who brought him to Everton in 2014 - admits he's seen one big change in Lukaku since his summer switch to the Premier League title chasers.

Martinez reveals big difference in Lukaku at United

"I have seen a difference in the maturity of Romelu since his move to Manchester United," Martinez admitted, per the Mirror.

“He is still a very young player but he has coped easily with the expectations and whatever Man United put on him.

“I can see he is really enjoying being in a team where there is very little margin for error.

“He is one of those players that sets himself little targets and you can see he’s on track."

Lukaku was left out of Belgium's World Cup qualifying win away to Bosnia and Herzegovina due to a knock he picked up against Crystal Palace last weekend.

Mourinho sweating on Belgian's fitness

And United fans were understandably upset when he reported for international duty, although he did not feature in the squad on Saturday evening.

However, the hope is Lukaku will be fit to face Liverpool at Anfield on Saturday in a match that Mourinho will be under huge pressure to win on two fronts.

Indeed, the Red Devils want to beat their close rivals, but Mourinho knows City could extend their lead at the top if they drop points, with the Citizens expected to beat Stoke at the Etihad.