Romelu Lukaku has conceded he struggled this season because he did not play with enough aggression, put on too much weight and felt tired after the World Cup.
The Belgian accepted he lost some of his pace because he had too much muscle and found it difficult to refocus on Manchester United after coming close to making Belgium world champions.
The £75 million (Dh350.5m) striker scored his first goal at Old Trafford since March in Saturday's 4-1 win over Fulham, and has now found the net in his last two starts.
But before then, he went on his longest goal drought for United, in a 12-game barren streak, and revealed he has had talks with manager Jose Mourinho in a bid to rediscover his form.
Lukaku, who scored 27 goals in his debut season at Old Trafford, was only a substitute for United's 2-2 draw against Arsenal and faces a battle to earn a place for Sunday's trip to Liverpool.
Mourinho used Marcus Rashford as his centre-forward against Unai Emery’s side and praised the Englishman for bringing pace and urgency.
“I think I just need to keep working hard,” Lukaku said. "Me and the manager had good conversations in the last couple of days, where really he told me what he wanted from me.
"And I know from my side I have to do better, and I just keep looking forward and improving, trying to add into my game and help the team to win."
Mourinho has been critical of some of his players’ efforts and attitude and Lukaku said: “I played with not enough aggression, I think. Not enough intensity.”
Lukaku scored four goals to help Belgium finish third in the World Cup, starring when they eliminated Brazil in the quarter-finals.
However, the tournament left him with a mental hangover. “It was intense. It was really intense because you get so close to absolute glory,” he explained.
Lukaku believes his problems were also partly physical after he scored 44 times for club and country in a marathon season. “After the World Cup, I think I really was like a bit tired,” he added.
"But, you know, I had the same thing in 2014 after the World Cup when I came back to Everton I was really in a slump.
"Me and the medical staff, we did like a lot of tests to see what the problem was. Also I had a hamstring injury, which is something that never happens to me."
______________
Read more:
Salah hat-trick against Bournemouth sends Liverpool top of the Premier League
Premier League predictions: Manchester City will prove too good for Chelsea
Andy Mitten: 'Mad dog' Marcos Rojo puts bite back into Manchester United
Newcastle United: Mike Ashley 'hopeful' of sale with four bids on the table
______________
Lukaku had bulked up for the tournament in Russia but has now adapted his training and diet to adjust to club football after he seemed to be labouring.
"At the World Cup, I just felt great and I think I played great over there, and then when I came back it is a different type of style. When you are in the Premier League, I cannot play with the same amount of muscle as international football.
"That was something that when I came back I knew straight away 'nah, nah, I cannot play in this style like this'."
"I had to lose muscle basically. So you just stay out of the gym, drink a lot of water, and [eat] a lot of veg and fish and it helps. Training differently [means] more prevention in the gym and more speed bursts in training and that's, for me, the most essential.”
United, who have already booked their place in the Uefa Champions League’s knockout stages, face Valencia on Wednesday. Mourinho has pledged to pick Paul Pogba, who has been dropped for their last two league games.
In the meantime, Lukaku took heart from the performance against Claudio Ranieri’s side as United scored four goals in a league game for the first time in a year and spurned other opportunities to make their victory even more emphatic.
“We should have scored more,” said Lukaku, one of those who missed chances. “All of us. But, you know, 4-1, it has been a long time since we scored four goals and just we enjoyed our football. I think Fulham didn't have one shot in the first half, so we showed what we could do.
"Everybody was really happy with our performance, but we have to continue like that."
