I don't know what the FA list looks like at the 3, but I can see why the Spurs FO was excited to get RJ into the mix and take their chances in a FA at the 4. There are some quality names on that list.
I like Gortat and Pachulia, but as someone said in another thread, there is a fear of the Spurs going TOO young and inexperienced. As is, we're already penciling in Hill and Blair (or Mahinmi/Gist) into significant roles. Add in RJ and FA Big into the list, and we're talking at least 4 players with very little experience in the Spurs system (include Mason if you'd like as he barely got to play with Manu last year)
The more I think about it, the more bringing Oberto back makes sense. Not to pick up significant minutes mind you, but to act as a coach/tutor/practice player to help the new bigs out.