The South American forward has reached the 300 mark when it comes to outings for the Blues.
He has spent six years in west London, being a regular under a number of different managers.
Willian has, however, entered the final 12 months of his current deal at Stamford Bridge and will become a free agent in the summer of 2020 if no fresh terms are agreed.
He continues to suggest that is open to extension talks, with the 31-year-old telling Chelsea’s official website when reflecting on his time in England: “I always believed I could play so many games. I had to believe.
“It’s difficult to achieve this number, especially when you play for a big club like Chelsea because there are many, many players that are fighting for the same position. It was a challenge for me.
“In football you have to prove yourself every day, in every game. When you stop doing that you have to stop playing. You have to prove it to yourself as well. I have done that.
“I have been here already for six years, I have had different managers, different players in the squad, and I was proving every training session, every game, that I can play many, many years for this club.
“I think I have improved a lot. Every game you can learn from. Then after every game you ask yourself ‘What have I done well, what have I not done well?’ I always want to continue improving.
“Now I’m very proud to reach this number, and I hope for 300 more to come!”