Football Football Dortmund splashes out on Mainz defender Diallo Abdou Diallo has completed his transfer from Mainz to Borussia Dortmund in a deal that will is said to be worth €28million. Tom Webber 26 June, 2018 19:36 IST Abdou Diallo has become Borussia Dortmund's second-most expensive signing. - Twitter @BVB Tom Webber 26 June, 2018 19:36 IST Abdou Diallo has become Borussia Dortmund's second-most expensive signing after his arrival from Mainz on a five-year contract was confirmed.Dortmund is understood to have shelled out €28million to snare the centre-back, eclipsing its outlay for Henrikh Mkhitaryan but falling short of the €30m spent on Andre Schurrle in 2016.Diallo impressed in his solitary season for Mainz, making 30 appearances in all competitions following his arrival from Monaco for a reported fee of just €5m."After getting to know the Bundesliga at Mainz, I am looking forward to the challenge of being able to prove myself at a club as big as Borussia Dortmund," the 22-year-old said."Together with my team-mates, I want to justify the trust placed in me and do my part to ensure that BVB achieves its goals in all competitions."Now I cannot wait to start preparing for the new season under Lucien Favre." Subscribe to our daily newsletter Get your daily dose of Sportstar with handpicked stories delivered right to your inbox! SUBSCRIBE Please enter a valid email address. Dugout videos