There will be plenty of guys out there, they won't be that exciting - Rasmus, Gomez, Holliday - but you could get them on one-year deals, possibly trade them if they work out (even Bourjos probably would have been traded if he'd been healthy, albeit not for much).
Ruf is all but gone. Asche isn't going to start or even platoon. I certainly still don't think they will sign a FA to a three-year deal, and probably not a two-year deal either.
But listen, if Ian Desmond was to somehow fall to them (or they just decided he was the guy and paid the money, a la the Nats and Werth), or they were able to trade for someone like Heyward (never mind his specific merits), nobody's really getting blocked. Might cost Williams and Altherr a little playing time for two months (as they'd have to share) but that's about it, and is still conditional (by August 1 Altherr may have come around or he may have sealed his future as a bench guy). Meanwhile, Quinn can stay in the minors (and try to stay healthy), Cozens is a year away. If everybody hits their upside and there's a logjam in 2018 someone (including Herrera) would be a valuable trade chip for another area of need.
I'm ready for hot stove, I do think there will be one major trade. And if they do acquire a player who in his mid-20s, he's not blocking somebody, he is somebody.