Fofana left ASSE for the Foxes for a fee rising to €35m.
Wantier wrote for L'Equipe: "Would Fofana have been worth more next year? We can project ourselves like that.
"But between the injuries and the form, there are too many imponderables. William Saliba unfortunately experiences it.
"The current context invites us to humility. Selling a defender who has played thirty professional matches for €40 million is a wise decision, in my opinion."