10. Roberto de Matteo (Chelsea; 2012):
The Blues lifted their first ever Champions League trophy along with the FA Cup in 2012 under caretaker De Matteo and it looked like it was the beginning of something huge at the Stamford Bridge. However, come November, after he was appointed as the full-time boss, Chelsea were going nowhere. They were poorly placed in the points table and were all but out of the Champions League in the group stage. This saw him get sacked on the 21st of November even before making it through the first half of the season.