At least that’s the verdict of Paul Ince, who’s spoken out in the build-up to the Red Devils’s showdown with Swiss champions Basel.
Belgium international Lukaku, 24, joined United from Everton this summer in a deal worth a whopping £75m.
And he’s hit the ground running at Old Trafford, scoring four goals in four Premier League appearances for his new club.
Lukaku is in line to spearhead United’s attack when Basel visit Manchester in the Champions League on Tuesday night.
And Ince reckons the hitman needs to impress in that competition to be considered among the world’s elite players.
Ince told the Daily Mail: "It is highly unusual these days for a £75m striker not to have had previous experience and, if he wants to be considered world-class, this is the stage where he has to prove himself.
"United's group opponents Basel, Benfica and CSKA Moscow will not be the acid test and he will not be fazed by them, but he needs to learn quickly so he is ready when the real elite stuff comes later in the season; knockout games against the likes of Barcelona, Real Madrid, Bayern Munich and PSG.
"Lukaku is a goalscoring machine and would cause problems to any defence in the world because of the way he runs at people and keeps his composure in the penalty area.
"On the other hand, his retention of the ball is not fantastic and, if he goes chasing the ball to get involved in the build-up, United could get punished because top Champions League teams exploit opponents who have lost their shape."
Lukaku has made four Champions League appearances during his career, all of which came at Anderlecht.
