It's well known that Chilwell was expecting to be a Man City player this season. He and his agent had agreed a deal with them back in April. It was only a last minute change of mind by Man City in the summer, when they realised that they were unable to move Mendy on, that prevented the move from happening.
I wouldn't be surprised if his head has been turned again. Chelsea and Man City are clearly trying hard to sign him, either now or this summer. We can deny that we're selling anyone as a club, but it doesn't stop a players representative from talking to that club and this could easily affect a young player.
He is playing like his head isn't right.