After joining the Blues from Anzhi Makhachkala in 2013, the Brazil international has established himself as an important part of the first-team squad and helped the club to two Premier League titles and one League Cup.
The 29-year-old believes that moving to England has helped him to develop a lot.
He said: "I've learned a lot in my time in England. I have been here for five years, so I've learned many things.
"English football is not simple and it is very different to others. I think it's one of the strongest leagues in the world.
"There's no doubt that to play there you can't just arrive and play with ease. You must also understand how English football works, understand the Premier League.
"I already liked the Premier League before playing for Chelsea, and there's no doubt that it has been a huge learning curve to me over these five years."