Sporting Lisbon president, Frederico Varandas, and sporting director Hugo Viana on Friday flew into London to hold talks with Manchester United, over Bruno Fernandes.
The Sporting officials are discussing a potential transfer for the midfielder, who they value at around £60million.
United were at the verge of signing the 25-year-old last week, while Tottenham were also interested.
However, Fernandes ended up staying at Sporting and even signed a new deal in November.
It is believed that United boss, Ole Gunnar Solskjaer and his assistant manager, Mike Phelan, went to watch Fernandes in action against Porto on Sunday.
Solskjaer refused to answer questions relating to the player on Friday.