Exhaustion has definitely played its role in their massive drop of form. Among the big European sides, Barcelona are the one who has done the smallest rotation while they have probably played almost the maximum of possible games in the last two seasons. They won the treble in 2014-15 by playing the maximum of 60 games they could play. From a maximum of 64 games this season, they'll play 61, that makes us 121 games out of possible 124 within two seasons.
But they're not the only ones who play many games throughout the season. We must also take into consideration that they had reached the sky in their previous season. Not only did they win all the trophies they aimed for in the beginning of the season, they also did it in style. They were deemed unstoppable, almost unplayable by the press and the majority of football fans. And therein lies the big question: What do you do when you've reached perfection? How can you improve on that?
Absolute success often clouds judgement. And, up to a certain point, this isn't illogical. It's not easy to start a debate about what could potentially go wrong when everything seems to be working fine and the first team looks like a well oiled machine. In times like that, the discussion is usually about the 2-3 squad players who should be signed just in case... And usually that's when the mistakes are made.
Winning the treble means that the players have played to their limits and it will always be difficult for the same players to retain the highest level of performance for a second season in a row. Barcelona has, beyond the shadow of any doubt, the best starting xi in the world of football. But the best starting xi doesn't equal the best squad too. But this is not as easy as it sounds, very few people would have been taken seriously, if they had proposed massive improvements on this Barcelona side. Plus most of these players are synonymous with the best era in the history of the club. It's never easy to let players like Iniesta, Pique, Mascherano, Busquets or Alves go and replace them.
Add to that the fact that they weren't allowed to sign anyone. Even if they approached someone, he would have to wait till January 1st to play first team football. They had no other option that to use the same players. Rafinha's injury only made things worse by removing one option in the midfield from Enrique.
And now we come to the front three. The MSN has played 16058 minutes in the last 12 months. Bayern's attacking triplet has played 2500 less minutes, City's 4800, Real's 5800 and Atletico's 6200 less minutes. They have played 4800 more minutes than the average of the main attacking options of the teams that are still in the CL this season... which makes us 53 more matches in the last 12 months!!! (stats belong to G. Marcotti of ESPN, who added up the minutes of the three most used attacking players in each side)
The Messi factor: We all know that he's one of the best footballers of all time in football but how important has he really been for them since he became a regular starter for them? Let's put it that way: Barcelona have won three CL titles with him as their focal point and they have been eliminated prematurely in the competition 7 times. 7 years and 14 games in the knock out phase in which they were eliminated (2007-Liverpool, 2008-United, 2010-Inter, 2012-Chelsea, 2013-Bayern, 2014 & 2016-Atletico). Do these 14 games have anything in common? In fact, they do. Messi hasn't scored in either of them, he has zero goals in these 14 games. The conclusion is that No Messi=No Party, no matter who plays beside him. And the truth is that Messi hasn't been his usual self since his return from international duty.
They have also been unlucky. In the game against Valencia they could have been out of sight after the first 25 minutes.
But i stand by what i mentioned earlier. It's almost impossible to improve on ultimate success. Once you achieve it, it's almost certain that it will take its toll on you sooner or later. And it's always better to face these questions early in the season than in the run in for all major trophies.