This may be an Orioles only thing, but I think I've seen it elsewhere.
Between innings, as the Orioles First Baseman (currently Chris Davis) runs off the field, someone from the dugout throws him a ball. It may be coming from somewhere else, because on TV the camera stays focused on him, and you can't see who throws it. I'm pretty sure it's the dugout though.
This has been happening for long enough - and consistently enough - that I'm sure it's a tradition or has some purpose.
Does anyone know what this is?