Here's my line of thinking (not to be confused with the Cubs' front office line of thinking): Sean Marshall is barely being used right now, thanks to the rotation stabilizing itself. The Cubs already have two long relievers available besides Marshall that are pitching well anyway (Hart, Lieber), and the lack of a lefty in the pen hasn't hurt them (in fact, it keeps Lou from using relievers like tissues to play the lefty/righty matchups). Also, the way Lou manages, the Cubs are regularly out of available position players well before the 9th (heck, they were winning 8-1 yesterday and had to use Marquis to PH), so having an extra position player available, even simply in a PH role, wouldn't be the worst thing in the world. In addition, it was pretty obvious that Ward has no business as a backup OF from the one time he was used there. He's strictly a PH/backup 1B at this point. So then, putting it all together, it would make sense to send down Marshall, get him some use as a starter to stretch him out as an available starter when the Cubs need one, and leave Murton up, giving the Cubs 14 position players and 11 pitchers.