Willian has confirmed in an open letter on social media that he is leaving Chelsea.
The Brazilian is out of contract at Stamford Bridge later this month, with Arsenal thought to be in pole position after making an offer of a three-year deal.
The 32-year-old was reportedly offered a new deal by Chelsea, but football.london understands the length of contract on the table from Arsenal is set to persuade the winger to move across London, with the Gunners increasingly optimistic of securing his signature.
Willian, who has spent seven years at Chelsea, had been in fine form for Frank Lampard's side since the season restarted in June, scoring four Premier League goals to take his season tally to nine.
But after the Blues' Champions League exit was confirmed on Saturday following the 7-1 aggregate defeat to Bayern Munich, Willian has announced that he has played his last game in a Chelsea shirt.
Posting on Twitter, the winger said: "AN OPEN LETTER TO THE FANS OF CHELSEA FOOTBALL CLUB.
"They were seven wonderful years. In August 2013 when I received the offer from Chelsea, I was convinced that this was where I had to play. Today I am certain that it was the best of decisions. There were so many happy times, some sad, there were trophies and it was always very intense.
"Yet, beyond the trophies, I learnt a lot about myself. I developed a great deal, becoming a better player and a better person. With each training session, with each game, with every minute spent in the dressing room, I was always learning.
"I am really grateful to the Chelsea fans for the affectionate way they welcomed me at Stamford Bridge and their support throughout my time at the club. There was also criticism, which is normal, what is important though is that both the affection and criticism drove me to always give my all in every training session, every game, to be constantly improving until my very last minute in a Chelsea shirt!
"The time has now come to move on. I am certainly going to miss my teammates. I will miss all the staff at the club who’ve always treated me like a son and I will miss the fans. I leave with my head held high, safe in the knowledge that I won things here and always did my best in a Chelsea shirt!
"My heartfelt thanks go out to all of you and God bless you!"
"Willian Borges da Silva."
Arsenal's contract offer is believed to be worth around £100,000-a-week with the guarantee of the third year a significant factor in the Gunners' favour.
Gunners boss Mikel Arteta is understood to be an admirer of Willian's talents and believes that the veteran playmaker can prove to be an experienced addition to an attack that includes youngsters such as Reiss Nelson, Bukayo Saka and Eddie Nketiah.
