TH added a blog post about this today. Basically DM says that given Prince wanting to play every day and Green's presence, there wouldn't really be any opportunity for him to play anyway. And it's not like he's going to be on the postseason roster, so if there are other opportunities they'll give them to Kotsay et al to prepare for the playoffs. You could certainly argue that Gamel should have been up much earlier, but it's not really going to matter much what 5 ABs he happens not to get in the last 3 weeks.