One of Ronald Koeman’s first acts as the Everton manager in June was the calculated risk of a phone call to Romelu Lukaku. You’re going nowhere, was the gist of the conversation with the striker with undisguised ambitions of Champions League football. Koeman got his calculations correct.

Lukaku’s latest goal, against West Ham United on Sunday, brought up his half-century for Everton in the Premier League and underscored his importance to Koeman’s ambitions at Goodison Park. The 23-year-old has scored seven and assisted three of Everton’s 15 league goals this season, equalling his best start to a Premier League campaign after 10 games, and credits clear direction from the new manager with an all-round improvement to his game.

It is a far cry from the fag end of Roberto Martínez’s reign when the Belgium international was more prolific at discussing a potential move from Goodison. Everton responded with a prohibitive £60m-plus price for their leading goalscorer and unless it was met, Koeman explained in the phone call, he would be expected to assume greater responsibility. The milestone of 50 Premier League goals is testament to the striker’s professionalism and refusal to sulk.

“When the manager called me during the European Championship I told him how I felt,” Lukaku says. “We had a really honest conversation and I was surprised how honest he was with me. He was honest in the way that he wanted to work and how he wanted the team to play. He saw me as an important figure and a big character. I just told him that whatever happens, I am a professional and I am committed to whatever scenario.

“I told him I am not a guy that is going to cause any problems. I am a guy who has to be at 100% and that is what I am going to do. He knew it straight away.

“When I came back in I was working more than ever before, to get fit and to do my best for the team. The first few games didn’t go so well but I was getting physically better. When I went with Belgium, I told them when I got back I would be at 100%. Since then I haven’t looked back. He is really helping me a lot with a lot of clinical advice.

“He was really clear in what he wanted to improve. Also the consistency. He has told me off only one time this season. It was in training and about the type of movements he wanted me to make. He was clear in his idea – there is a real clarity about what he wants on the pitch. That helps me. I have never started a season so well.”

On Saturday Everton travel to Chelsea, who were interested in re-signing Lukaku last summer but not for an asking price that dwarfed the £28m they banked for the Belgium striker in 2014. “It will just be a normal game,” says Lukaku, with a giveaway laugh. “If clubs are interested in you it is a compliment to the club you are playing for. It means that Everton have done great work with me. The motivation for me is the same whether it is Man United or Bournemouth.

“I want to win the game and be part of a team that is going to be successful, and that is what we are trying here. There will be ups and downs and we have to be much stronger at Chelsea. We are talking about a top side with a top coach.”

Lukaku’s third assist of the season enabled Ross Barkley to seal victory and cap an encouraging individual display against West Ham. It was Barkley’s first goal in eight matches, a period marked by inconsistency and criticism from Koeman, and the former Chelsea striker believes the midfielder’s omission from recent England squads stems from a lack of goals and erratic decision-making.

“I think the manager has been hard on him because he knows Ross has the quality – he just needs to be more productive,” Lukaku says. “When we do finishing or have small games in training, I tell him to keep his eyes open and play with his head up. He can see much more then, he can see where the space is and he can play the pass or shoot himself. The decision-making has to be better. When he gets that, you are talking about a fantastic player.

“At the minute the players who play in his position for England – like Dele Alli and Wayne Rooney – have goals in them. I think Ross has to get more goals and more assists than he has been doing. If he does that he is going to play. To me, if Ross fulfils his potential you are talking about the best player in English football. He has got everything.

“He has got power, technique, he can shoot with both feet, he is fast and he can pick a pass. The manager has been working with him so he makes the right decisions on the pitch. Who is going to stop him?”