RP not Advancing

[Swindy10]

All-

I am in a league where RP’s advance in grade to the first batter they face. Through the seasons I’ve noticed if a RP comes in during the inning, say two runners on, none out…they don’t advance. My thought was, OK, the RP didn’t advance because there weren’t any outs. But, that theory has been proven untrue in some other recent games. Can anyone explain this one to me?

Thanks
Mark

[TSBL]

they only advance if they pitch from same side as batter ie left vs left.