Francisco Liriano and Rey Olmedo being added to the roster meant that someone needed to exit from the bullpen to make room for Philip Humber, even if he'll probably never actually sit down there.
With the bullpen holding two semi-effective lefty rookies, Leyson Septimo and Hector Santiago seemed to be the two men at risk, but Santiago had a lot of advantages. Hector has been on the team all year, and his misguided ascent from Spring Training surprise to the top of the bullpen was reflective of the confidence the organization has in him.
After sticking with Hector through some monstrous stretches of homer problems, the Sox are sending him down now after a month of July where he skirted around control problems to post a 1.50 ERA. Surely there would need to be a specific reason for the Sox to bail on Santiago at this moment.
Well for one, Hector hasn't displayed a platoon split of much significance, and with right-handed reinforcements popping up all over the place, the long relief outings where he's proven himself might be all he has left. Even that work could be getting soaked up by 6th starter Philip Humber, if Chris Sale returns to regularly scheduled outings.
Speaking of 6th starters, there's no 7th starter at the moment. Dylan Axelrod and Simon Castro are both on the Charlotte Knights disabled list, and Pedro Hernandez--not that another start from him would be especially welcome--is in the Twins organization. If it was at all possible to stretch him out, five innings of Santiago would be preferable to the other options. Sure enough...
Santiago will work in a starting role and stretch out a bit
— Scott Merkin (@scottmerkin) July 30, 2012
Getting tabbed as the next guy to start out of the organization isn't high praise, and while Kenny Williams has discussed Hector Santiago's future as a starter, that's a pretty optimistic projection for him. His control and command are not the greatest, and while he's not too young to develop, he's had a hard enough time keeping hitters guessing as a reliever, let alone multiple times through the order.
The difference between Septimo and Santiago in the pen is likely a lot smaller than than the difference than Santiago and God-Knows-Who in a spot start, though. That's what important, right?