Not every game is going to be a walk in the park for Barcelona, and not every opponent are going to try every trick in the book in order to influence the match officials and help them win the game.
For 90+ minutes on Saturday night Leganes were horrible to play against. Spiteful, nasty and intent on getting a rise out of their opponents at every possible opportunity.
It was impossible for Barca to get their natural game going to any great degree, and though the visitors were the better side, they were dragged down to the level of their opponents for long periods simply because that was the only way to play successfully against them.