United manager Jose Mourinho is said to be a big admirer of Willian and would love to bring him to Old Trafford, but he will now have to meet the Blues' demand for him to have the Brazilian.
Fellow Brazilians Philippe Coutinho and Paulinho already ply their trade at the La Liga champions and Willian admits the trio get on well.
Willian has been heavily linked with a move away from Chelsea in recent weeks.
"Paulinho and Coutinho are great players, and friends".
He scored a late goal to take Colombia's meeting with England into extra-time, but it was not enough to help see them through.
Willian admits he's following reports linking him with a move to Barcelona but is unsure if he will leave Chelsea this summer. I've not received any information about that.
Recently, Willian who is now in Russian Federation for the World Cup has been linked with a move away from Stamford Bridge with Barcelona also interested in his signature. I'm trying to focus on my performance, playing for Brazil'.
In fact, if we are to think about the swap, it should be Chelsea who should pay us for Martial and throw Willian into the deal.
According to Mundo Deportivo, Barcelona may try to decrease the financial expenditure it would take to recruit Willian by offering Yerry Mina as part of the deal.
It is unlikely there will be any movement on Willian's future until Sarri has been appointed and the player is no longer involved in the World Cup.