The Argentina international scored 13 goals last season and his performances have attracted interest from a number of suitors.
Sunderland have been heavily linked with the 26-year-old and some reports had even claimed they were ready to make a £21m bid.
However, according to A Bola, the Black Cats will have to fight off competition from Italian giants AC Milan.
The Serie A side have identified Salvio as one of their top targets this summer and they have made contact with Benfica over a possible transfer.
As well as Milan and Sunderland, Monaco have also expressed an interest.