Would never give up too much talent for a rental, i.e, Zach Grienke. Although I agree Grienke could help us giving up some of the very few prospects we have for basically a two month loan would be silly and I don't think duquette will allow that. I'd say package Reynolds, Betimit, and Flaherity, possibly Pearce or Tolleson, and see if the Padres bite at that. We all know 3B, along with other positions, is a defensive black hole. And offensively lacking at time, acquiring Headley could be a decent fix to those issues. With slim prospects to deal sending two veterans to a team with some young stars could be helpful. But the Padres are asking for a lot for Headley because they are rebuilding.
We all should keep in mind that we can't strip clean the farm to acquire rentals for two months, Grienke and Hamels. Rumors have been spreading about Wandy Rodriguez of the Astros and I've heard talks about Shaun Marcum being available as well. Pitching would be nice. I agree. But with upgrading defensive issues and offensive slowness could help improve the starting pitching. As they would no longer feel like they, the rotation, would not have to go out and throw zeros every inning.