#6 Frank Lampard
Frank Lampard, the man that helped bring silverware to the club was allowed to leave Chelsea after 13 magnificent seasons with the club. The all-time leading goalscorer for Chelsea, Lampard was considered one of the greatest midfielders of his generation. The Englishman, to the shock of many Chelsea fans, signed for title rivals Manchester City in 2014.
Lampard was old and well past his prime but still wanted to play a role in the club – Mourinho though had other plans. The Special One, although not happy with the fact that Lampard wanted to join rivals City, still sanctioned the move. He was left ruing that mistake as Lampard scored a late equalizer against Chelsea at the Etihad which could have potentially cost the Blues the title.