Sarri selected the 29-year-old as his captain for a 0-0 International Champions Cup draw with Lyon at Stamford Bridge on Tuesday, a fixture which required penalties to determine a winner as Eden Hazard struck the decisive spot-kick upon his return to action with the Blues.
Chelsea are now set to turn their attention to a Premier League opener on Saturday, with a trip to Huddersfield Town's John Smith's Stadium up first.
Willian is happy to be back in a Chelsea shirt and looking forward to that contest, with the Brazil international of the opinion that new boss Sarri is capable of delivering silverware this season.
"Of course, I am ready. I have to improve more in the physical aspect but I feel good," Willian said in response to Goal at Stamford Bridge. "I felt good today to play around 65 minutes, it was good for me and I am ready to play this season.
"We have to look forward because we have a lot of games this season and we want to win titles. He is a great manager, he is an intelligent manager. He works a lot and we will try to improve. Of course, we have just started. We are right at the beginning but we can do good things this season."
The Blues winger may have been unsure of the reception he would receive at his home stadium upon his return to post-World Cup action, with Sarri calling it strange when a passport issue led to him being him being late back from Brazil for pre-season.
Willian was in constant communication with Chelsea, but the timing of the saga was not ideal as it came on the back of strong rumours linking him with a move elsewhere after five years in west London.
However, he was roundly cheered by the Stamford Bridge faithful against Lyon and was happy to be back in familiar surroundings.
"It is always good to play at home," added Willian.
"It doesn’t matter what the game is or against who, it is good to play at home. It is good to come back here. It is good to feel the atmosphere from the fans. I think we did a great job here today."