Former Belgium midfielder Radja Nainggolan has questioned whether Romelu Lukaku can return to his best.

Lukaku is with Belgium at the World Cup, having struggled with a thigh injury since returning to Inter Milan on-loan from Chelsea this past summer.

Antwerp midfielder Nainggolan said: "A footballer becomes more susceptible to injuries from the age of 30. Before the age of thirty I could continue running, but now it is no longer so.

"Romelu is more explosive than I am and if he can no longer play with that force, he is no longer the real Romelu.

"I doubt he will continue to wear the Belgian shirt for a long time, because at a certain age you also think about your body."