"He (Lukaku) had a really tough start to the 2014-15 season after the World Cup. He was catching up with his fitness until January, but we knew that he was a footballer who could reach those heights," Martinez told the club's website (www.evertonfc.com).
"The reason is that he is someone who can run with the ball and has incredible finishing with both feet. He is powerful, has got real strength and his back-to-goal play has improved immensely.
"In 2015, he gave consistent levels of performance and it is what we expect to achieve in 2016 as a team. That will be the target."
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Lukaku amassed a third of his 54 goals for The Toffees this season, ending 2015 with 31 goals - the highest in a calendar year since Bob Latchford netted 57 in 1977, according to the club's website.
"You look at the amount of chances he gets in every game and it shows a really good understanding of the team mates around him who are providing him with that service to always be a threat," Martinez added.
Everton, who are 11th in the table, begin the New Year against fourth-placed Tottenham Hotspur on Sunday at Goodison Park.
(Reporting by Nayan Das in Bengaluru, editing by Pritha Sarkar)
