Celtics vs. Heat Game 1 thoughts?

Why is it that everyone blames a loss on a player having a bad night instead of saying the opposing team just had bad defense? I'm a Celtics fan and every year in the playoffs, whenever Lebron or some other All-Star in a team does poorly, it's because they had an "off night".

Why can't it be because the Celtics are just that strong of a defensive team? Isn't it their defense that kept Bosh pressured the whole game and thus scored poorly? Isn't it the Celtics' stifling defense on Wade that kept him from coming out stronger than he usually does (as we saw las year in the 1st round?) Isn't it also why Lebron performed poorly in the playoffs last year (Celtics lead in forced TOs last year?)