The Belgian striker has been in fine form for the Red Devils since joining Jose Mourinho’s team from Everton back in the summer transfer window.
Lukaku has slotted aimlessly into the first team at Old Trafford since his move and has already scored 10 goals for his new club in all competitions.
Manchester United fans will be hoping to see Lukaku continue his brilliant form as the season progresses.
However, former Manchester United defender Neville has warned Lukaku that he is in for his first real test as a Red Devils player on Saturday at Anfield.
Speaking to Sky Sports, Neville said: “Romelu Lukaku has settled in brilliantly and done everything he was asked to do in terms of converting those home draws into wins, but games like this one are the real test.
“When I look back to the Everton striker’s recent performances at Anfield he didn’t play well, so this is the next step up for him.
“Going away to Anfield is a big test and his service will be more limited so he’s now got to show the ruthless streak to win the big games for United.
“He will be defined by his performances in big matches. You’re at a club with aspirations of winning things and a world class striker will be defined by trophies and performances in big matches.”
Manchester United have made a brilliant start to the new Premier League season, after having won six of their seven games to leave them second in the table and level on points with leaders Manchester City.
The Red Devils are aiming to win the Premier League title this season for the first time since their final triumph under Sir Alex Ferguson back in the 2012-13 campaign.
Mourinho led Manchester United to Europa League and League Cup glory last season.
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