Southampton are chasing Porto defender Bruno Martins Indi.
The Holland international played for Saints boss Ronald Koeman at Feyenoord and only left for Porto in the summer.
Koeman is keen on a reunion and Lisbon sources state contact has been made with the player's camp about a January move.
However, Porto are reluctant to part with the Dutchman this month, though things will change in June.
Martins Indi was part of Louis Van Gaal's World Cup squad in the summer.