oh yeah, i'd make that trade even with the notorious injury risks of both nelson cruz and josh johnson.
aside from the injury risks, nelson cruz an fall off the face of the earth for a month or so at a time (much like he did b4 his DL stint) but then he can also get hot-as-feces and carry your team for 2-3 weeks at a time. this guy is trying to buy low on carl crawford, and hey, if you're able to trade him for two injury-riddled stars, that's something to go for. i consider corey hart a fantasy nothing here, as if you're on the ball you can usually come up with some sort of a hitter to provide stats close-to or even better than his... hell, even tho he's fallen off as of late, if you took a flier on lance berkman by now you got more production than maybe even 2-3 months of corey hart would give you.
josh johnson was looking like one of the best pitchers in baseball b4 the injury, and perhaps was even the frontrunner in the cy young category. i don't have to go on about him as you know what you'll get.
as for SBs, man, i see every day that rajai davis (~18-20 SB) and coco crisp (18SB) and juan pierre (10SB and like 10CS) are STARTED in only 33-38% of leagues, so like, there's a lot of people either not owning them or merely not starting tehm, so odds are you can wing a deal for one of the "lesser" SB guys and make up those SBs cuz you're going to come out ahead on this trade.
i don't know how long josh johnson is out for, or if this will be one of those ~2-3 week injuries that gets stretched out to ~4-5 weeks, but i'd roll the dice and take the better players and cash out on C-dub and take what you can get.
i am not part of the cult of ryan zimmerman so i can't endorse that move... i think he's the very essence of "fantasy-overrated" so i'd be hesitant to go and get him, cuz even when he is around i marvel at how he consistently ends up being a late-2nd/early-3rd round draft pick... i see it as a fantasy positive cuz that's one more player i'd never take getting selected instead of other players i would take.