Almost every season, when the Champions League matches get underway, fans ask the same question. "Who is capable of beating Barcelona?". Despite their dominance in La Liga, Barcelona's success in the Champions League has been somewhat erratic and with only three wins in seven seasons, it could be said that they have in some respects, failed to live up to expectations.
Their success has been part of a Golden era of Spanish football with the national team winning both the World Cup and European Championships in succession.
Barcelona players have formed a huge part of that Spain side which has swept all before it, and the passing, possession type play is a feature of both teams. However, last Wednesday night, we saw another illustration of where the Barcelona machine can be derailed.
Having been involved in and around football for close to 45 years, I've seen some great sides rise to the top of the game and then fall away almost as fast as they got there. Real Madrid, Liverpool, AC Milan, Ajax and Manchester United have all dominated European football for a time and then fallen from grace.
Without a doubt, the most dominant club side in the world over the past 4-5 seasons has been Barcelona, but are they about to go the way of so many other top sides? Following the Catalan's 2-0 defeat to AC Milan on Wednesday night at the San Siro, fans across Europe are asking if their castle is beginning to crumble?