The Super Eagles striker has played a key role in Napoli's title push this season, after registering 11 goals and three goals in 20 appearances.
Osimhen's form has seemingly caught the eye of some of Europe's elite clubs, with the likes of United, Los Blancos, Liverpool and Arsenal reportedly keen.
However, any side wishing to make a move for the Nigeria striker would not fork out €100 million for his services, according to Spanish outlet Fichajes.
Serie A legend Alessandro Altobelli had some high praise for the Nigeria, who joined Napoli from Lille two years ago.
“Osimhen is stronger than (Dusan) Vlahovic,” Altobelli said, as per Corriere dello Sport.
“When I criticized the Nigerian (earlier in the season), he had only scored 4 goals. Now, (Napoli coach Luciano) Spalletti is working hard on him, forging him into one of the best strikers.
“On Sunday I was able to see his movement, as well as the goals. In this moment he is enjoying great growth. And, for me, he is better than Vlahovic.”