#1 Petr Cech
Mourinho decided to replace Petr Cech – Chelsea’s bedrock during their glory days – with the youthful Thibault Courtois. Cech had been the Premier League’s best keeper for several years, but his form was expected to decline in the following seasons. The young Belgian was well on his journey to become one of the best keepers in the world. It seemed a logical move to offload Cech at the time.
After being benched in favour of the Belgian, Cech moved to London rivals Arsenal in the 2015/16 season where he was statistically the best keeper of the season with a better save to goal ratio than any other keeper in the league.
To make matters worse, Courtois was ruled out of the 2015 calendar year in September with a long term injury. Although Cech could not help Arsenal win the league, he was still responsible for their title challenge. On the other hand, Chelsea finished 10th in one of their worst seasons in recent football history.