I'd just like to add that :
The majority of the Celtics losses this season are
a) Against bad teams (Wizards, Cavs, Pistons, Bobcats, to name a few)
b) On back to backs.
This one against Indy is a combination of both.
Why again is anyone really surprised?
The Celtics rarely put in much effort against poor teams like this, if you don't know this trend already you clearly haven't been watching the Celtics these past few years.
Their game against the Spurs this week will speak a lot more about what's happening, WAYYYYY too early to hit the panic button (wait for a playoff loss or two before you start doing that).