Borussia Dortmund's ascent to the top of the European game has been built on the unlikely. When they were meant to lie down and be beaten, they proved everyone wrong. And yet, now that they have cemented their status as one of the continent's most feared opponents, they struggle to live up to the standards they have set themselves.
Ever since Jurgen Klopp took over in 2008, they've been producing surprises. Fans could scarcely believe the run of one defeat in seven months which proved the catalyst for their 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 their seemingly unstoppable progress: themselves.
