I don't see Spurs as underdog here. It's just that Nuggets are up in the overall standings.
They are 2-2 in regular season so we can't really say who's the dominant team here.
And what's the difficult part of choosing who will passed the second round?
Game 1 Spurs
Game 2 Nuggets
Game 3 Spurs
Game 4 Nuggets
Game 1 to 4 have an alternate result. Meaning each game, they can be dominant over each other.
Anyways, I bet for Nuggets @ 6 in one of the competition thread here so although I like the game to reached at Game 7 and it's hard to imagined that Nuggets will have a 3 game winning streak against the Spurs, I will be biased here for now and expecting Nuggets to sealed the game in today's match lol.