Another round of semifinal questions

What a night. We got to see a tense, nail-biting defensive clash followed by a tense, nail-biting offensive clash. And in the end, the team down 3-1 wasn't the one we expected.

So with the defending champions on the ropes and the Eastern Conference champs looking suddenly vulnerable, it's time for another edition of four questions -- in which I go around the league addressing one big question from each playoff series. Let's start at the top and work our way down:

What's up with San Antonio's defense?