Spurs have told Real Madrid that Nuri Sahin must be part of any deal for Luka Modric, according to a report.
The Spanish champions have set their sights on Modric after boss Jose Mourinho accepted it would be impossible to prise David Silva from Manchester City.
Tottenham chairman Daniel Levy rejected three bids from Chelsea for the Croatian last summer, but has signalled he is now willing to listen to offers for the midfielder, who wants to leave White Hart Lane.
Initial talks with Real Madrid about a cash-plus-player deal have already taken place, reports the Sunday Times.
Spurs have apparently told the Spanish club they will need to pay £25million and part with Sahin if they are serious about signing Modric.
Levy, who is renowned for his ability to negotiate large fees when selling players, knows he can take a tough stance, as Paris Saint-Germain are also lining up a sizeable bid for the Croatian.
Turkey international Sahin only moved to Real Madrid from Borussia Dortmund in an £8million transfer last summer, but he failed to settle and hardly featured in their La Liga title triumph.
Despite a disappointing first season in Spain, the 23-year-old remains highly rated and was voted player of the year in his final campaign in Germany, when he played a key role in Dortmund's Bundesliga title success.