Nelson's agent has confirmed that two clubs, one English and one Spanish, are keen on the Benfica right-back who has reportedly attracted interest from Liverpool.
The right-back has been vastly impressive for his Portuguese employers so far this season and his performances in the SuperLiga and UEFA Champions League have seen him earn a first call-up to Luiz Felipe Scolari's international squad.
Nelson's displays against Celtic this season and Manchester United last term have also drawn interest from Europe's biggest leagues, with Rafa Benitez reputed to be his most persistent fan amongst a clutch of English admirers.
The Reds boss is searching for another right-back to challenge Steve Finnan after seeing Jan Kromkamp leave Anfield over the summer, and has reportedly included Nelson on a shortlist that also contains the names of Blackburn's Lucas Neill and Sevilla's Daniel Alves.
Benfica are believed to be demanding around é¼25 million (£17 million) for the player whose contract runs out in 2010, and his agent Ulisses Santos has revealed that there are currently two clubs interested in his client.
Liverpool are understood to be one, with the other an unnamed party from La Liga, and Santos believes the two sides will be keen to enter into talks at the end of the current campaign.
"Two clubs are interested but the subject is down to Benfica," said Santos.
"Now these clubs have decided to follow the work of Nelson and to speak at the end of the season."