Martinez has said the signing from Chelsea hasn't been 100%, and needed competitive games to build his fitness.
The Everton manager has explained the possible reasons why the 21-year-old has yet to find the form of last season, but thinks his best form is not too far away.
He told the Liverpool Echo: “The situation we have is that he was unable to get a full pre-season after the World Cup and the knock he had so early in the season meant we couldn’t allow him to have a proper introduction into work.
“He had to get himself fit by playing games and now we’re paying for that.
“We all need to understand that he is still doing a good job for the side and he will get to a position where he is 100% fit and he will be able to enjoy his football.
“At the moment he can’t enjoy it and he can’t be the player that we all know he can be but that doesn’t affect him too much because he’s a responsible guy. He’s got an incredible desire to be successful for the team."
Last season, Lukaku was a menace for the very best opposition defences as he struck 16 times for the Toffees. He showed his promise at West Bromwich Albion the season before that but it appears he wasn't going to get the first team opportunities he would've liked at Stamford Bridge, so he opted to make his loan move to Goodison Park permanent this term.
The start to the season has been a pretty poor one for Everton which sees them sit just above the relegation zone after seven games, though they haven't had the easiest set of fixtures. Martinez will be hoping that Lukaku's form, along with the side as a whole, improves over the coming weeks as they look to build some momentum which helped them finish with a Premier League record points total for the club last season.
There have been signs that Lukaku and Steven Naismith have linked up well, and with the early season form of Naismith this season, the Scot could take some of the burden of the Belgian, and together they could be a formidable duo for any opposition to handle.