The striker could be available for as little as £5.8m, although the Premier League pair will likely face competition from Turkey.
The striker has enjoyed a solid season for the Portuguese outfit, scoring 13 goals in all competitions, with 10 in 19 appearances in the league.
That has led to interest in his services building from a number of clubs, with Everton and Bournemouth in the Premier League and Turkish duo Galatasary and Besiktas all said to be monitoring him. His end of season form in particular is believed to have revived interest in the player.
He currently has two years remaining on his deal with his current side, so they are in no desperate need to sell, although the report suggests that they would do should any potential deal be lucrative enough for them.
They are thought to have set an asking price of €8million for their man, which would work out at around £5.8million for the Premier League duo. Neither they, nor the Turkish sides, would be interested in that price though, despite it being far below his release clause of €30million.
Everton in particular are said to be after another forward this summer to help ease the load on Romelu Lukaku, who struggled in the Premier League last year but was prolific in the Europa League.
In contrast, Bournemouth are keen to add to their squad ahead of their first season in the English top-flight.