Darin Ruf made a rehab start last night in Clearwater, the last of the Phillies reinforcements from the injured reserves to do so. That puts a lot of pressure on Ruf, who has never played a full season or produced consistently at the Major League level.
Presuming the "Darin Ruf is an Outfielder Now" experiment remains a chilling, but closed, chapter in Phillies history, there's only one position that makes sense for him (As was the case when he was trying be an outfielder): first base.
As Matt Gelb points out, the Phillies first base slash line is 13th in the NL in all three categories: .226/.292/.395. Ruf was projected by Fangraphs to slug around .407 and forge an OBP of .316 this season in a limited number of at-bats. This spring, he went 10-for-46 with five walks before straining his oblique. Last night in Clearwater, he went 0-for-3 with a strikeout.
Ruf is no savior, but can he contribute in any helpful manner? The bench, while rid of Freddy Galvis for the moment, remains weak. Ruf is more of a power option who isn't worth much defensively, much like Ryan Howard. Sending him back down to triple A isn't going to do him much good, other than get him at-bats at a level where it is already known he can hit.
If the Phillies wanted Ruf that badly, it would make sense logistically to replace John Mayberry , with Ruf taking over as the backup first baseman, and Tony Gwynn Jr. able to provide depth in center field. But assuming Ruf needs time to acclimate and it's not until a couple weeks later that he's even got his timing down consistently - while dancing around re-aggravating that oblique - do the Phillies really have space for another .210-.230 hitter getting at-bats, whose ceiling is .250-.260 once he gets straightened out?