When you're the defending Cup champs, everybody brings their "A" game against you when you're on the road (and too often at home). It's a big deal for their fans and so the players give it their best.
For the defending Cup champs, not so much. It's a struggle to play at such a high level on a long road trip and basically you end up getting up for some games and sleepwalking through some others.
Know this all too well from how Vegas went through last season as the defending Cup champs. Some nights you play like Tarzan, and some nights you play like Jane.