Literally every trade where we gave away future assets for near-term players, unless I'm forgetting about a bunch of playoff series wins that made them all worth it.
Like it's easy in retrospect to say we'd rather have back Luzardo, Treinen, Vazquez, Giolito, Lopez, etc. etc. etc.
We got Doolittle and Madson for Luzardo and Treinen. Doolittle and Madson have been more valuable than both of them. Doolittle alone has been worth that. Treinen has one good season that he doesn't appear to be able to replicate.
We got Melancon for Vazquez. Melancon was a rental and panned out well. It's easy to say well, we should have kept Vazquez, but he was struggling here.
Sure, it'd be nice if Rizzo had a crystal ball and knew that Eaton was going to have a major injury here in DC. But I don't see how he's supposed to predict that. In 23 games, prior to injury in 2017, Eaton accumulated 0.5 WAR. That's roughly 3.5 WAR season. It's safe to say that Eaton is a ~3.4-4.5 WAR player if he stays healthy. For a guy who until this season, couldn't put up an ERA under 4.
The Nats have actually "cashed in" on all of their trades except Eaton. And Eaton was due to a fluke injury.