Once a game begins, if there's a rain delay, the umpires have control over the decision-making when it comes to how long the delay will last and if the game will be postponed.
Prior to first pitch, however, that decision rests with the home team.
Last night, the Nationals could have decided to try and wait out a heavy rain, sitting through a lengthy delay and then attempting to play the second game of a three-game set against the Marlins.
Instead of doing that, however, the Nats opted to postpone the game, a contest which will not be made up either today or tomorrow, when both the Nats and Marlins have off.
There were likely a number of factors in this decision.
First of all, the Nats were getting word that lots of rain was coming, and that it would fall for quite a while. Instead of risking injury to any players moving around on a wet field - or risking a multi-hour delay that could drain players physically and mentally - the Nats chose to postpone the contest and try again tonight in the series finale.
By postponing the game, however, the Nats also will push this contest back until a time later in the season, when they (hopefully) will be healthier and have more of their key pieces on the active roster.
Last night's scheduled Nats starter was Blake Treinen, who has made two career big league starts. Treinen has done a nice job and all, but you would think the Nats would prefer to have one of their more seasoned, accomplished starters get the ball on any given night.
The Nats are also obviously without Ryan Zimmerman and Bryce Harper in their lineup, two key middle-of-the-order bats that they hope to have back by the All-Star break.
Manager Matt Williams announced last night that Treinen will now move to the Nats' bullpen for the time being, and the team will go with Jordan Zimmermann as tonight's starter. Zimmermann will start on normal rest, and Treinen will provide extra depth in relief.
For whatever reason, Zimmermann has fared better in his career when working on normal rest (a 3.03 ERA in 62 starts on four days' rest) compared to extra rest (a 3.90 ERA in 61 starts on five or more days' rest).
Having Zimmermann get the ball in tonight's game keeps him on his normal turn and skips the rookie Treinen for this turn.
The Marlins aren't scheduled to return to D.C. until Sept. 26-28. It's possible that last night's game is rescheduled on a mutual off-day prior to then, but it might just get tacked on to that scheduled three-game series that is set to end the regular season.
It wouldn't be ideal to have a doubleheader on any of those days with playoff spots potentially on the line, of course.
But the postseason picture might already be determined by then, and given the conditions last night, the pitching situation and their overall team health at the moment, the Nats might have figured they'd be better off just bumping last night's game back in the schedule and dealing with it later in the year.