Lukaku joined Manchester United from Everton for an preliminary £75million in the summertime.
The 24-year-previous has scored seven instances in his first seven video games for his new membership, together with 5 within the Premier League.
Martinez is aware of Lukaku smartly from his time in fee at Everton and now as Belgium supervisor.
He says United boss Jose Mourinho will lend a hand Lukaku give a boost to much more over the approaching years.
“It never crossed my mind that it would be something difficult for Rom,” Martinez informed talkSPORT.
“Everyone that performs with him or works with him realises in no time that he has an elite mind.
“As a footballer, you’ll have your attributes however the point of interest he will have is somewhat distinctive.
“When he went to Manchester United he was only fascinated with beginning smartly and making a large have an effect on and that’s what he has achieved.
“He continues to be an overly younger participant – occasionally we overlook he’s simplest 24 – however his goalscoring report is sensational and he’s a participant that desires to elevate on growing and elevate on finding out.
“Now he’s with a supervisor (Jose Mourinho) with whom he’ll continue to learn other sides at membership stage.
“I’ve noticed a large distinction with regards to his adulthood when he comes to global camps.
“From the younger participant I signed from West Brom and Chelsea at the moment, it’s the similar goalscorer however with an unbelievable adulthood.
“That is superb to see and he nonetheless has many, a few years to expand.”