Borussia Dortmund's ascent to the top of the European game has been built on the unlikely. When the club was meant to lie down and be beaten, the club proved everyone wrong. And yet, now that it has cemented its status as one of the continent's most feared opponents, the team has struggled to live up to the standards it has set for tiself.
Ever since Jurgen Klopp took over in 2008, Dortmund has been producing surprises. Fans could scarcely believe the run of one defeat in seven months which proved the catalyst for a title win of 2010-11 and when it looked like order had been restored and Bayern Munich held a healthy Bundesliga lead the following year, they were able to turn the table on the Bavarians and retain their crown.
It has been a brilliant, romantic story, but there has always been one obstacle standing in the way of the club's seemingly unstoppable progress: the team itself.