Willian rejected Tottenham Hotspur to join Chelsea from Russian outfit Anzhi Makhachkala for £30 million ($39 million) in 2013.
The former Barcelona player has been with Chelsea for four seasons and was part of the Premier League title winning side in 2017. The 32-year-old also won an FA Cup and Europa League title.
Premier League: Chelsea manager Frank Lampard feels creative winger Hakim Ziyech will help them 'unlock the door'
“Trying to come in the top four is the priority for us so my main concern is that," Lampard said.
Harry Wilson, Pedro hit memorable strikes as Premier League giants Liverpool, Chelsea win pre-season friendlies
Welsh international Harry Wilson gave Jurgen Klopp a reminder of his talents with a spectacular goal as Liverpool defeated Lyon 3-1 in a pre-season friendly on Wednesday
Premier League: Cesar Azpilicueta insists Jorginho will eventually silence crictics ahead of Chelsea's clash against Watford
Cesar Azpilicueta insists Jorginho will eventually silence the critics because the much-maligned Chelsea midfielder is reaching peak form ahead of the Watford clash.
Europa League: Pedro's away goal gives Chelsea slim advantage in semi-final tie after score draw against Eintracht Frankfurt
Chelsea set a Europa League record of 16 successive matches unbeaten on Thursday with 1-1 semi-final first leg draw at Eintracht Frankfurt thanks to a Pedro equaliser on the stroke of half time.
Maurizio Sarri rode his luck as Chelsea narrowly avoided humiliation at Cardiff to hit back and snatch a controversial 2-1 win.
Premier League: Chelsea manager Maurizio Sarri says dropped Kepa Arrizabalaga still his first-choice goalkeeper
Maurizio Sarri believes Chelsea's crucial 2-0 win over Tottenham can save their season after his decision to drop Wembley rebel Kepa Arrizabalaga paid off on Wednesday.
Carabao Cup final showed Maurizio Sarri is Chelsea's man to keep for reasons far beyond his tactical masterclass
Chelsea may not have won the Carabao Cup on Sunday, but the game provided the Blues with enough evidence that Maurizio Sarri is the man to keep for things beyond much beyond his tactical performance.
Premier League: Chelsea would need to sell an established winger to satisfy Callum Hudson-Odoi's wishes, says Maurizio Sarri
Maurizio Sarri says Chelsea would have to sell one of their established wingers in order to satisfy Callum Hudson-Odoi's desire for immediate first-team action
Premier League: Chelsea must stay calm to rediscover form of early season, says winger Pedro Rodrigues
Chelsea’s season hangs in the balance after Monday’s FA Cup exit but they must stay calm and recapture their best form in the next two games to turn things around, winger Pedro has said.
FA Cup: Imperfect Chelsea, Manchester United seek validation of renewed approaches in enticing cup tie
When Maurizio Sarri’s Chelsea clash with Ole Gunnar Solskjaer’s United at Stamford Bridge in a withdrawn FA Cup fifth round tie on Monday, it will all be about validation of their relatively newfound approaches and systems.
Premier League: Chelsea assistant-manager Gianfranco Zola denies neglecting talented youngster Callum Hudson-Odoi
Zola believes Hudson-Odoi still has plenty of room to develop and would be helped by staying at Chelsea to learn from fellow wide-men Eden Hazard, Willian and Pedro
Premier League: Willian says he has no intention of leaving Chelsea despite rumours of potential exit
Willian has been repeatedly linked with a move away from Chelsea but he was adamant he wanted to stay at the west London club.
Premier League: Eden Hazard has potential to become Chelsea's greatest player ever if he stays, says Gianfranco Zola
Hazard has been strongly linked with Real Madrid after the Belgium star refused to rule out a move to the Bernabeu and admitted playing for the Spanish giants would be a dream come true.
Premier League: Arsenal win explosive North London derby; Chelsea bounce back with assured victory over Fulham
Arsenal secured a memorable 4-2 victory over rivals Tottenham to move above them in the table, as Chelsea moved back into third place by beating Claudio Ranieri's Fulham.
Premier League: Chelsea ride on Alvaro Morata's brace to sink Crystal Palace, move to second place in the table
Alvaro Morata scored twice to take unbeaten Chelsea above Liverpool into second place in the Premier League behind Manchester City on Sunday, but Maurizio Sarri's men made hard work of seeing off Crystal Palace 3-1.
Premier League: Chelsea need more than Eden Hazard's brilliance to beat Jurgen Klopp's full-strength Liverpool side
Liverpool in the Premier League, however, are a completely different proposition as they remain one of the true contenders for the Premier League this season alongside Manchester City, while Maurizio Sarri's Chelsea are the outsiders.
Europa League: Chelsea manager Maurizio Sarri says Pedro's shoulder injury in PAOK win not as damaging as feared
Chelsea boss Maurizio Sarri has played down the significance of the shoulder injury Spanish winger Pedro suffered during the 1-0 victory over PAOK Thessaloniki.
Premier League: Maurizio Sarri believes there's more to come from his Chelsea side despite a winning start to the season
Maurizio Sarri believes there is far more to come from his Chelsea side despite making it four wins from his first four Premier League matches in charge with a 2-0 home defeat of Bournemouth on Saturday.