The player was due to return on Monday following his exploits with Brazil in this summer's World Cup.
He said: "I don't know if he is not confident".
The Brazilian could be on his way out of Stamford Bridge after being linked with Real Madrid and Manchester United. I will see them on Saturday for the first time so I don't know the situation in this moment.
Chelsea manager Maurizio Sarri has ruled off an exit for Blues' striker after he held talks with him, according to reports. Reports claimed that an expired passport had been the reason for Willian's delayed return to London.
The Chelsea boss also confirmed Callum Hudson-Odoi was a part of his plans for the new campaign after his impressive display against Arsenal in Dublin.More news: Korea Constructs New Missiles While Trump Claims Denuclearization Success
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Hudson-Odoi did play a couple games towards the end of last season.
Chelsea lost the match against Arsenal but Callum Hudson was excellent out wide and created all sort of problem for Hector Bellerin and ultimately get a penalty from him which is wasted by Morata. "We made a mistake in the last minute, but I'm really happy with the performance", the Italian responded when asked why he was happy despite the loss.
"He has a fantastic team, fantastic players and squad - I think he has conditions to do good work". "We have to wait". But in the future he will be a very, very strong player.
We can never read too much into pre-season friendlies but it's a bonus to catch a glimpse of how preparations are going with the new season just around the corner.