Lukaku, 24, arrived at Old Trafford in the off-season with a massive £75m (R1.3b) price-tag weighing on his shoulders - but the Belgium international has silenced his critics with 27 goals and seven assists in 49 games across all competitions.
However, the form of the robust striker hasn't been enough for the Red Devils to challenge their cross-town rivals for the title this season, which Lukaku feels is down to consistency and not the strength of the current playing squad.
"I'm really confident in my team-mates. I think we can do it with the team we have now, but we should have shown more consistency throughout the season," he told reporters after the FA Cup win over Tottenham, as quoted by AS.
"For us now it's up to us to be more consistent and the manager needs to see if he has to add more players, but with the players we have now, I think we have enough.
"It was a strange season for us. If we had more consistency we could have been up there with Manchester City now. But we know what we have to improve for next season and winning games like this is what we do."