Willian has lavished praise on Brazil national team coach Tite.
Though the Brazilians have not been in the best of form during recent years by their standards, they are one of the pre-tournament favourites to win the tournament, which takes place in Russia this summer.
Willian is also likely to be a key part of the Brazil team which will play in the event.
About his national team boss, Willian said: "Tite's arrival was definitely important. He's a very intelligent manager who brought us many ideas; someone of great ability," Willian added.
"I think to me he's one of the best coaches in today's football, both for what he has done and for what he's doing right now with Brazil.
"He's definitely a coach that has changed our game style, our game patterns, both with and without the ball. So, this is all helping us a lot on the pitch."