Cech believes Willian has silenced the critics and is hard to drop given his form.
He told the London Evening Standard: "The questions were raised because he came from Anzhi Makhachkala where he was unlucky with injuries so he didn't play much. Everyone was saying 'Chelsea bought a player who didn't play'.
"But from day one since he came here, he has worked really hard. He was waiting for his chance and since his first start you can see he is taking his opportunity.
"He has been absolutely brilliant. He keeps working for the team, making the difference, scoring goals, defending. I thought I'd never see anyone running more than Ramires but he's really there.
"It's fantastic to see he's enjoying his football, enjoying his life in the club. This is important. He can only get better. You always give players a few months to settle because the Premier League is different to anywhere else. It's very pleasing to see his progress."
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