The Nats get Yovanny Cruz, Jake Bird, Ben Grable and Jack Cebert.
Cebert is the one the Nats are probably most hopeful for - a starter that probably ends the season Top 10 in the Yankees prospect lists. One of their college arms that they turn into decent prospects. He ruled High A then struggled in AA but might be turning that around too. The main issue with Cebert is that he turns 25 next year so when a true stud should be rounding into major league form, he'll likely be proving he deserves a call-up from AAA. That is where he sits though - maybe he's a major leaguer maybe a AAAA type. But never hurts to have more of those as options.
Grable is kind of a one-trick pony in that he has a fun fastball that is tough to hit... for minor leaguers. It was DOMINANT in high A but more hittable in AA. It's gonna be one of those things that if it it holds that major leaguers find it hard to hit he'll be a great relief arm. If not he's probably nothing. But hey you want someone with a chance!
Cruz is your "dynamic stuff can he ever control it?" type. At about to be 27 it's far more likely that the answer is no BUT if it is yes he could be dominant.
Jake Bird is 30yo bullpen filler that is probably a safe bet to be out of baseball in under 5 years, maybe under 3.
The MOST likely single scenario - Jake Irvin and a couple of live bullpen arms that give you hope and maybe a good year but ultimately disappoint, but we're talking like 20% here for MOST likely. There are a lot of different possibilities. If the Nats get Grable or Cruz to become a lights out reliever then it's worth it. If they get Cebert to be a good enough rotation guy, it's worth it. And the chances are probably better that one of them has a career at least sort of like this.