What defensive-minded player is available that would take us over the top? None. Marion is a ghost without Nash and Raja's D is overrated. While we have performed offensively against the mediocre to horrible teams in the league, we have performed poorly against the top teams in the league, offensively speaking. So, our strength is stymied against teams that actually have good defense. I'll take a Ray Allen on this team quicker than I'd take a Ben Wallace when you consider the team as a whole.
Right now, when we are getting burned by Terry or Ginobili or Williams (Deron) or any role player who comes in and blows by Raja for 30 points, we have no answer (speaking about the top teams). Yes, we can overcome poorer teams and their role player scoring outbursts, but the Suns have not proven they can overcome the D from top teams (see record against Spurs the last few years, see the Mavs games this year, and look historically at the major come-from-behinds the Kings have laid on us).
Like I said, I'll take a player who can CONSISTENTLY (ie, not Raja and Diaw) keep things open for Amare and Nash and Barbosa on O. If our shooters are off, which they have a tendency to do against the top teams, they collapse on Amare and double to Nash effectively grinding us to a halt. We all know how D'antoni would (not) use a defensive presence who is a black hole on offense. So, all things considered, a better offensive player would work better for this team....