^
I can't recall which poster it was (apologies) but someone said yesterday how it's not tiredness, it's lethargy. I think that poster was correct. The good thing is that you cannot beat tiredness without physical and mental rest, but you definitely can shake off lethargy, and a kick in the pants often does the trick with that.
Edit: I don't mean that as a criticism of the team or manager either.
We've been so good for so long, and built up an incredible lead, and it's quite normal for a relative malaise to kick in at some point, even if it's only on a subconscious level rather than conscious. At some point, an opposition side will hit form and take advantage. We then get the opportunity to reset and go again.