The 29-year-old's situation at Stamford Bridge has been a constant source of speculation all summer due to his lack of playing time at the west London club last season.
Brazil's exit from the tournament after a 2-1 defeat to Belgium in the quarter-finals means Willian can now turn his attentions to his club future.
"Well, they are excellent players with a lot of quality", Willian told the Evening Standard when asked about potentially linking up with Brazil teammates at Barcelona.
"Manchester came to me, they talked with my agent, but nothing happened, because Chelsea would not negotiate me in any way and I'm very happy at Chelsea".
"People speculate a lot".
The Brazilian coming to United will add another dimension to our attack and will make us more potent, however, losing Martial would be a major blow as the Frenchman has a lot of potential.
But, with the Blues snubbing a £50million bid from Barcelona for Willian, the Red Devils and Mourinho may have to offer more.
Anthony Martial's relationship with Mourinho is not all good right now, but it is unlikely that the Frenchman will leave the club as United wants a huge fee for him and there are not many clubs interested in paying that gigantic sum.
With the Brazilian and the Blaugrana reaching an agreement, it is now just for the two clubs to reach an accord before the player officially becomes a Barca player.