Martinez admitted that he believes Lukaku's future still lies at parent club Chelsea.
"Every time I speak to Chelsea they rate Romelu really highly and I think that's always been the case," he said.
"They made a massive investment on a player they always felt was going to take three, four, five years to be ready.
"We are just happy to have Romelu and all I want is him to develop a good memory at Everton."
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