Spo doesn't have a lot of other options, his players aren't producing. If Bosh and Wade get hot, then maybe it disrupts the Spurs on D. But they haven't, and it isn't. Everything Spo throws at the monster gets crushed. Lebron scored 19 of his 28 in the third quarter tonight, and the Heat lost the quarter by 5 - on a night when Manu, Boris, and Duncan combined for 25 points.
The Heat need production, and their stars are gassed and their role players aren't as good as the Spurs' role players because they're all a bunch of talented guys assembled because they're talented, not because they fit the system. Players that know their role and are good at filling it are more powerful than talented players put on the court together. The Spurs aren't unbeatable, but they have to beat themselves more than Miami can beat them.