Chelsea boss Maurizio Sarri has insisted that Willian will not be sold in the January transfer window, amid reports Barcelona are ready to sign him.
The Catalan giants were interested in the winger last summer, making a total of three bids, with the club's final offer thought to be more than £55m.
Despite suggestions that Barcelona had now proposed a deal which would see Willian's Brazilian compatriot Malcom move in the opposite direction, Sarri was adamant that the 30-year-old would remain at Stamford Bridge.
When asked about Barcelona's reported interest, Sarri said (as quoted by Sky Sports News): "I didn't receive anything yesterday. I have no idea.
"You have to contact the club and ask about the market, because if you ask me about the market, you put me in trouble because I don't know how to answer. As you know, Willian for us is very important.
"I think he can do better, he can do better because of his potential but he is really very important to us, so I think it is impossible to lose him in January."
Aside from Willian, speculation has intensified over Cesc Fabregas' imminent departure to AS Monaco, with Sarri revealing that the Spain star's frame of mind means he will not be considered for the Blues' Premier League clash with Newcastle.
The Chelsea manager added: "You know very well my opinion as I told you in the last press conference. I think he that he needs to go.
"At the moment, for his mental condition, he is not able to play I think. I don't know the last decision of our club but at the moment he is not able to play. I need a replacement but I don't need a very important player like Cesc unhappy here."