Kevin De Bruyne
Chelsea brought the Belgian from Genk for a measly £7 million, and immediately sent him on loan to Werder Bremen for a year. Though he returned to the Bridge hungry to compete, after an inconsistent first half of the season, Wolfsburg signed the unsettled De Bruyne. The rest is history. He contributed to 10 goals and 21 assists, a Bundesliga record in his only full season at the Volkswagen Arena and signed for Manchester City for £55 million in 2015.
Since his exit from Chelsea, he has scored 59 goals and has 96 assists in 230 matches. He was also City's most prominent player as Pep Guardiola's team marched to the title in the 2017/18 season.
Thorgan Hazard
Eden Hazard's brother signed for Chelsea from Lens a couple of days after his brother joined the Blues. While his brother has thrived in the club, Thorgan never got to play for the Blues. His loan to Borussia Monchengladbach for the 2014/15 season was very effective and the German club exercised the option to buy in 2015. He has 30 goals and 30 assists since his departure from Stamford Bridge.