Thursday's loss to the Mets was just a ballgame. The Nats still won two out of three, so they won that series. It's a long season, and winning series is what keeps you in first place.
Last night's game is also in a sense 'just one loss', thought it's the type of loss that can have psychological implications for the whole ballclub. Being up nine runs in the middle innings with your ace on the mound is never a game that should be lost.
So today, zero runs through the seventh. Great pitching by Sheets, or a psychological carry-over from last night?
One thing's for sure-- I don't think a team has ever won a game in which they were shut out. Also, losing the first two games of a four-game series (should that happen) means there will be no series win, and then the onus falls on them to at least make damn sure there's no sweep, as a sweep would only add to any downward psychological implications for the team.