According to Revista de la liga, there are concerns about Messi off the field in the past year or so, part of the Ronaldinho and Deco saga. Apparently Messi was the only one to miss the last training session before christmas, and then was late to the first training session of the new year - and there was a young Barcelona player who Ballague speaks to, who spoke of the same concern he had about Deco and Ronaldinho in the dressing room, with regards to Messi too.
They were also saying that once a player sees how important to a club they are and what they can get away with, its hard for them to turn back. This would of course be something that applies to Ronaldo too.