Jose Altuve has done what Jose Altuve does and so it’s World Series time again, the Astros back for the second time in three years, the Nationals there for their first time in infinity years, so we return to our annual exercise: who was the greatest Astro/National? (Last year: the greatest Red Sox / Dodger.) By which, just to have a good pool of players to work from, we mean Astro/National/Expo? This time the answer’s uncontroversial: it’s Rusty Staub. I think of Staub as a Met, because that’s what he was when I was a kid, and that’s who he played the most seasons for, but Staub came up with Houston and spent three years of his prime (and, much later, 38 games of his non-prime) in Montreal. I never knew this guy was so good! In 1969 he had a .426 on-base percentage and hit 29 home runs, a lot back then, and got one measly MVP vote.
Anyway, Staub put together 17.4 WAR in his three seasons in Montreal and 13.1 more in 6 years with the Astros. Good satisfyingly balanced answer this year.
If you restrict to players who played for the Nationals, not their Quebecois predecessors, the pickings are a lot slimmer. Looks like Justin Maxwell and Mark Melancon are the best bets. I guess I give the edge to Maxwell just because he played multiple seasons for each team.