To me, it's not so much that they're using last year as an excuse, its more the weight of expectation that they're finding hard to deal with.
Last year, they achieved beyond their wildest dreams and throughout that season had nothing to lose at any point. If they had fallen short, they would still have had the best season this club has had in living memory. Understanding this, they played with no fear and it showed game after game.
As Champions, they have it all to lose. I now see a team riven by fear. Fear of losing what they had and it brings a tension to their play that didn't exist before. Its not that they're not trying, they seem to be trying too hard rather than letting it come naturally. In any sportsman or team, that's usually a recipe for failure.
None of this team (possible exception Huth) have had to deal with this before and I think that's a real problem.
If we can survive this season, I believe we will see a return to something like our best form once the level of expectation has been adjusted and the fear goes from their game.