I dunno, but it's a good question. The only thing that saves RJ is that he's not a bad player. I just believe he was miscast onto a team, whose style didn't fit his skills. Combine that with the fact that he has a horrendous contract, this lead to unreasonable expectations of him. Now don't get me wrong. The boy doesn't have much heart and is somewhat of a mental midget, so that's his fault. However, the NBA is filled with overpaid, underachievers who have no heart. It's just unlike the Spurs to acquire them.
For the record, Charles Smith was on the decline when he arrived in S.A. He didn't make the ridiculous money that RJ made, but he was often disappeared and played like he had rigor mortis most times - like RJ.