Anderlecht could make a January bid for the striker, with the obvious attraction of European football.
Scouts were at Easter Road in abundance during Sunday's impressive 2-1 win over Rangers when Riordan scored one of the goals.
Hibs put the 22-year on the transfer list in the summer after he rejected an offer of a new contract. His current deal expires next October when he could leave the club as a free-agent.
