The 25-year-old wing-back, who rose to prominence playing under Villas-Boas for Porto, is highly rated, especially after enjoying a successful Copa America tournament with Uruguay and also playing a part in his country reaching the semi-finals of last summer's World Cup.
"The only thing I can confirm to you is that we have made a bid for him and we are very far apart in terms of numbers," said the Portuguese.
When asked if he was confident a deal could be done, he added: "Not very confident."
Primarily a left-back, if Pereira arrived it would potentially cast doubt on Ashley Cole's previously unquestioned place in Chelsea's team.
Source: PA
Source: PA