4. Cesc Fabregas

Cesc Fabregas has been instrumental to the club's fortunes ever since he arrived, contributing immensely in the two title-winning campaigns through his assists and goals. But he now on the wrong side of 30, and many would consider him as the weak link in Chelsea's midfield.
Sarri's attacking philosophy and the high pressing game means Fabregas's game time will be slightly limited this season compared to the other three midfielders. Though very good on the ball with superior vision, his work rate is definitely not up to the manager's demands.
Despite that though, Fabregas is a crucial figure and can do an important job from the bench when the team needs him.
Chelsea will play in the domestic competitions as well as the Europa League. Having a player of Fabregas's caliber and experience will certainly be a bonus.