Top teams starting to look flat, unmotivated, tired, banged up, etc.
Underdogs with nothing to lose are starting to gain experience with their youth, settling into more of a rhythm and getting comfortable with playing time at this level.
Plus, the weather's getting colder.
Happens every year -- just like August in baseball. Be careful of heavy chalk, teasing big numbers or expecting a superior team to blow someone out. Not going to happen as often as it has been.