Willian is taking legal action after being the victim of an alleged fraud over his Chelsea future.
The Brazilian has been linked with a move away from Stamford Bridge with Manchester United and Barcelona both keen.
He is yet to return to pre-season training but has taken to social media to reveal he has been the victim of identity theft.
A letter purportedly sent from a representative claiming to act on behalf of Willian, emerged appearing to grant another representative permission to discuss a move for the player.
The letter, with FIFA logos on it, claims to have been signed by the Chelsea star - but he has denied any involvement and confirmed legal action has been taken.
"In the recent days I have been informed that a “letter of authorization for player agent FIFA”, allegedly signed in my name has been circulated through the football market," the Brazilian's Instagram post read on Thursday.
"In such letter, Mr. Denirobson Dias would grant an authorization to Mr. Renee Pinheiro Anunciação to represent me until 15 August 2018, throughout football clubs in the United Kingdom and France.
"I would like to clarify that I never signed such letter, the content of which I completely deny.
"Finally, since there seem to be clear evidence that my signature has been forged, or anyway misused, I hereby inform that my lawyers are already instructed to proceed with all appropriate legal measures before any competent courts or authorities.
"I hope I have clarified the matter and any possible misunderstanding."
Willian has been linked with a £65m move to Manchester United to reunite with Jose Mourinho.
But last week, he insisted he was happy at Chelsea and was not considering his future.
He was involved in a bust-up with former boss Antonio Conte at the end of last term but will be given a fresh start under Maurizio Sarri.
Chelsea are yet to comment.
Nesaiknruy
110
Can we stop linking evey Chelsea player with a move to every club in the universe. Kinda getting sick of it now knowing that apart from Courtois, no one else is actually anything close to leaving since the words out of Hazards mouth have been spoken for like 4 seasons straight and the Willian links all came up after he covered Contes face with trophies which has nothing to do with him having problems with Chelsea themselves.... Hazard knows he's the main man in Chelsea and he won't be the main man in any of the club's that he's linked with so he will stay. Willian is like one of the most loyal players so unless the club push him out he won't leave and frankly if you're a true Chelsea fan you don't want to see him go.
begongq
86
It all seems very shady that he returns late and has this released. He obviously has been pushing for a move, seemingly feeling like he won’t get it, has changed his mind and is now trying to deny everything or make excuses such as his passport.
Handsome Mike
83
Oh my! when I got a notification "Willian takes legal action" my heart started racing already! Thought it was a legal action against Chelsea lol.
DönRichie1
72
William Borges is very naive Guy; someone is using you're mandate in you're absence why can't you question you're management team including you're agent whom I strongly suggest he has a hand in this
hakbilmns
65
Willian thanks for putting the records straight concerning your future. I am one of your fan and very happy to see you future still Lie's with our great club Chelsea. Rex Amere Ejumudo, Lagos Nigeria.
Nababelpz
30
I am really tired of all these transfer rumours about Chelsea players. I just want to make things clear; allow those players that want out to go and use players that are hungry to play for the club to continue.
woaelnt
24
Willian has decided to stay and Chelsea supporters should give thanks to God, the Creator. Now the important thing is for him to join his colleagues in training in order to fit in the teams formation of play. I hope the coach will forgive and cooperate with him despite his long absent from training. We all love Chelsea and wish the coach and the team the best of luck in the coming football season. I know it will be well by the grace of God.
Nesaiknruy
21
I love to see him in Chelsea shirt
He's been in a Chelsea shirt for ages????