Manchester United manager Louis van Gaal has refused to rule out the possibility of signing goalkeeper Victor Valdes.
Manchester City boss Manuel Pellegrini says he is confident that England goalkeeper Joe Hart will sign a new contract.
The 22-year-old impressed at the World Cup finals with Holland and that saw a number of clubs linked with a summer move for his services.
But Porto are set to land the imposing defender in a deal worth around €8million, although Martins Indi would not reveal which club he would be joining.
"It's true that I am leaving, but now it's Feyenoord that will have to say more about the subject," he told RTV Rijnmond.
Feyenoord, who have already sold Graziano Pelle to Southampton this summer and look set to lose Stefan De Vrij and Daryl Janmaat in the coming weeks, have bolstered their squad with the signing of experienced Dutch international Khalid Boulahrouz, who returns to his homeland from Danish outfit Brondby.
Technical director Martin van Geel told the official Feyenoord website: "With Khalid we have signed a very experienced and good defender.
"He is fully fit and can play in various positions in the defence. With his experience and qualities he can give great value for the development of the younger players in our squad."