Lukaku spent last season on-loan with Roma and is wanted at Napoli by their new coach Antonio Conte.
But Giuseppe Falcao, now a local pundit, told Radio Kiss Kiss: "I can only speak well of him, for me he had an important season in Rome. I'm not just talking about the numbers and goals scored, but also about the role he had in the team. What is certain is that I have some doubts about moving from Osimhen to Lukaku: I think it's a step backwards, Lukaku is born in 1993 while Osimhen is a footballer on the rise.
"Maybe take Lukaku and invest in other parts of the pitch, of course it's an overall discussion but between Osimhen and Lukaku, even though I love Big Rom, we're talking about two different players and today Osimhen at best guarantees you 20 goals in the championship.
"Let's say that as a club, Lukaku is a non-returnable investment: he is not Inter's Lukaku, less devastating and he cannot be resold."