Romelu Lukaku's first coach has admitted that he finds watching his former protege frustrating, but concedes he may be partly responsible for the Everton striker's flaws.

Ariel Jacobs was in charge of Belgian giants Anderlecht when Lukaku made his senior debut as a 16-year-old and continues to watch the striker on a weekly basis as part of his television commentary duties.

And he sympathises with those fans who have been left exasperated by the Belgian international's hit-and-miss performances for Chelsea, West Brom and Everton.

"I still regret that we didn't take more time to work on some of his weaknesses because I still see them now," Jacobs is quoted as saying by the Liverpool Echo. "But everything went too quickly for him. 

"The fact is, he didn't give us time to work on those weaknesses because he was important to the team.

"He is improving already but sometimes I still see him have an awful game but then suddenly the striker is there, he scores and helps his team to overcome a problem.

"He may have been playing badly and you feel like he is not in the game but, and I know in my experience, he is suddenly marvellous and he scores, which is the most important thing."

The Antwerp-born forward scored 10 Premier League goals for Everton last season after signing for a club record fee of £28million, but Jacobs says he still doesn't know if the 22-year-old has what it takes to be ranked among the best in the world.

"It is difficult to predict if he will be the best striker in the world, but he is only 22 and, given everything he has been through, that should be an advantage," he added.

"He's played for Anderlecht, Chelsea, West Brom and now Everton – that is what a 27-year-old should have done, not a 22-year-old.

"He is showing what he is able to do for Everton and if he is really good then it will come."