@OaklandCertified is right, wear and tear will be a factor for the Celtics.
You don't just get over the physical and mental toll of a hard-fought Eastern conference run in four days. That shyt can take a whole offseason; we really don't know what state the Celtics are in. That's one big factor playing in the Warriors favor, is that they really haven't been pushed in any capacity. On the flipside of that, the battles the Celtics have gone through can be a factor for them, because they know what it takes to play through adversity, and this Warriors squad, as a collective, doesn't yet.