#9 - Mario Gotze
A product of Dortmund's academy system - German wonder-kid Mario Gotze was promoted to the first team by Jurgen Klopp in the 2009-10 season.
In the following years, the precocious talent formed a wonderful understanding with fellow team-mates such as Marco Reus and Robert Lewandowski and helped Dortmund win back-to-back Bundesliga titles.
And then Bayern struck!
On April 23rd 2013, barely 36 hours before a crucial Champions League match between Borussia Dortmund and Real Madrid - it was announced that Bayern had activated a 37 million Euros release clause and that the player would be joining them the following season. Bayern Munich would go on to beat Dortmund in the final with an 'injured' Mario Gotze looking on.
Gotze scored 36 goals in 3 seasons under Pep Guardiola helping Bayern win 3 League titles, 2 FA Cups and a Super Cup. During this period he also scored the winning goal in the FIFA World Cup final in 2014 against Argentina.
However, this story has a happy ending for Dortmund fans. Gotze returned to the club in 2016 and claimed that 'he regretted his move away' from the club. Although it must be stated that he has never reached the same heights as a player since.