I'll meet you half way. You do realize Splitter is playing against backups. He struggles mightily on offense, doesn't have a jumpshot, struggles to create his own shot, can't rebound or block a shot on defense, and sometimes looks like a deer caught in headlights. If he doesn't know the system, there is no point in putting him out there. That's what practice is for. You may not believe in Pop's system, but he produced 4 championships and was .4 tenths of a second and a bad foul by Ginobili away from a possible 5-peat.
Duncan didn't struggle to get minutes, neither did Elliott or Robinson. Yeah, I know, they're exceptions to the rule. However, he struggles to get minutes because he doesn't know what the he's doing, and when he does get an opportunity to play, he doesn't impress. If he's not impressing in games, it's quite possible Splitter's not impressing in practice. Why would you stick a guy out there who constantly struggles during a time when the Spurs desperately need wins to combat a brutal second half schedule. The old saying "we need Splitter to beat the Lakers" is false. He doesn't matchup well with Odom, Bynum or Gasol. He would be destroyed by the Lakers front court.
On a scale of Mahimni to Scola, he is much closer to that of Mahimni.