3) Shinji Kagawa (Borussia Dortmund to Manchester United – £17m)
The Japanese international wasn’t exactly an expensive purchase by the Red Devils but the disappointment stems from the fact he had been a very good player for Dortmund before his arrival at Old Trafford.
Kagawa scored 17 goals and provided 14 assists in 43 appearances during the 2011/12 season but he managed just six goals in 57 games for United over a two-year period before returning to Dortmund in 2014.
