Napoli have acquired defender Mario Rui on an initial loan from Roma with an obligation to buy, the Italian clubs announced on Thursday.
Roma said that the initial year-long loan will cost Napoli €3.75 million, with another €5.5m set to be paid to make the move permanent if "certain sporting targets" are met.
Rui, 26, only moved to Roma last year from Empoli, though a cruciate ligament injury kept him sidelined until January.
He only made nine appearances in total last season.