But Mitrovic has failed to come to grips with football in England's top-flight so far, having found the back of the net just three times in 15 appearances for the club.
"I remember Lukaku when he was a young lad and he was the same size he is now. He's every effective. He's had to develop and now he's looking like a real deal, the complete centre-forward," McClaren told British media.
"Mitro is developing and is a few years behind, but Mitro has his own game. He needed to come out (of the side) for a few games.
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"He's done that now and has his focus and energy and intensity back. He needs to score more goals. But he was bought as a development (player) and someone with potential, and that's how he's playing at the moment."
Mitrovic, who started his last two games on the bench, is likely to return to the starting line-up against Everton because of an injury to Papiss Cisse.
McClaren has reminded the Serbian to control his emotions after the 21-year-old picked up three yellow and one red card so far this campaign.
"He needs to hold that emotion and control it, but we should never take the aggression out of his game. He has bullied defenders -- he did that against Chelsea (in September). That's what we want from him," McClaren said.
"There are a lot of things he has to work on and get right. He's got talent and all the ingredients, he just needs to pull it all together."
(This corrected version of the story clarifies McClaren is Newcastle United manager)
(Reporting by Shravanth Vijayakumar in Bengaluru)
