Tottenham could sign Ricardo Pereira for less than his £22m buyout clause.
Porto are prepared to negotiate a lower transfer fee for the 23-year-old, who Spurs are considering as a potential replacement for Kyle Walker at right-back.
Walker is wanted by Manchester City and an approach to Spurs is expected imminently.
Pereira is one of a number of replacements Spurs are discussing and an intermediary involved with the player has said Porto do not insist on his buyout clause being met, and as little as £13m could be a “realistic” transfer fee.
Pereira has spent the past two seasons on loan at Nice, where he has emerged in the top-three performing players in his position in Ligue 1.
The Portugal international made 29 appearances and scored two goals last season as Nice finished third in the French top flight.
Spurs have scouted a number of potential replacements for Walker, including Ajax’s Joel Veltman, Bayer Leverkusen’s Benjamin Henrichs and Hoffenheim’s Jeremy Toljan.
Veltman is on holiday following international duty and will sit down with his representatives to discuss his future when he returns in a fortnight.
Henrichs, who is also of interest to Manchester City, signed a new long-term contract in May, making an affordable transfer for Spurs more difficult to agree.
Toljan is about to turn out for Germany’s Under-21s at the European Championships, at which Spurs will have three of their top scouts watching players.
Tottenham are also interested in Fulham left-back Ryan Sessegnon.