Willian has revealed Oscar has said goodbye to his Chelsea team-mates ahead of his proposed move to Chinese Super League team Shanghai SIPG.
Oscar has struggled for game time at Stamford Bridge under Antonio Conte and announced this week that his switch to the CSL, which will reportedly making him the world's highest-paid footballer, was "90 per cent done".
The transfer is yet to be officially confirmed, but Willian has already bid farewell to his fellow Brazil international.
"[Oscar] has already sad goodbye. A great friend is leaving, but we wish the best for him and his family as well," Willian told ESPN Brasil.
"A player's career can be quick, so when such an opportunity comes you think about your family. You want to be prepared for when you have to stop playing."
At a news conference on Friday, Conte confessed he understood Oscar's decision, but questioned his ambition.
"Before the money must be the passion, the passion for football," Conte said at a news conference.
"We started to play when we were children without money, only passion. Then came money, but the passion is more important than money for me. If you have not got that passion, it is no good.
"Oscar is a really good player. I was very proud to have him in my squad and have him as my player.
"I am proud of his attitude, his commitment and his behaviour, which have been fantastic. I have great respect for every decision made by a player. If you ask me, 'Are you sorry?' then yes, I am sorry. I am sorry because he is leaving as a really good player and a really good man.
"But I understand him and his decision. As a player, you have to take the best decision. Sometimes you can say no, but other times you have to say yes. They are offering a lot of money. Maybe you only think about it for one second or 10 seconds, but it is very difficult not to think about it if the offer is amazing."