Son Heung-min
Hamburg were initially unwilling to sell Çalhanoğlu to other German teams, but their purchase of Pierre-Michel Lasogga from Hertha Berlin made such an exception no longer financially viable. On 4 July 2014, he left Hamburg for league rivals Bayer Leverkusen, signing a five-year contract for a transfer fee of €14.5 million. His actions leading up to the transfer caused some controversy, including taking sick leave from Hamburg; he justified the leave by saying that he was stressed by aggression from fans, including vandalism of his car. He also criticised Hamburg's director Oliver Kreuzer, accusing him of betrayal. The move was later criticised by Son Heung-min, as a response to Çalhanoğlu calling his former Leverkusen teammate's transfer to Tottenham Hotspur "badly advised".