I don't think Pop has done a very good job of late managing Ginobili's minutes as of late. Ginobili is best when he plays 28-30 minutes when everyone is healthy. If Duncan, Parker are both are injured, I think you have to fight the urge to play him more and actually play him a bit less. 25-27 minutes if Ginobili is the focal point of the offense the whole time makes more sense and gives the Spurs a better chance to win than to play him 30+ minutes and make him dead tired in the fourth.
I also I don't think it's a coincidence that Ginobili has struggled since Parker's ankle became an issue. Parker was ineffective against Golden State and then hasn't played since. Those are the four games in which Ginobili has played poorly. It's not really that Parker creates a huge amount of shots for Ginobili, it's more that Parker's penetration has to be accounted for at all times and that opens lanes for Ginobili.
Without Parker, teams can send extra players at any Ginobili pick and roll. They don't do that with a healthy Parker because if you are scrambling, that's when Parker is able to get easy layups.
Bottomline is I don't think there's much reason to panic regarding Ginobili. The beginning to this season for Ginobili wasn't a fluke. I don't see any reason why he can't return to that level once Parker is back and teams can't simply concentrate on keeping Ginobili from slicing up their defense.