That's why any series win here (3-1 or a sweep) would go a long way to getting the Nats the East crown they want. It's starting to get late in the year, to the point where it's harder to lose that ground once you make it up. Just look at last 7 games. Nats weren't on, Mets were. Mets gained two games. At that pace they'd need to play 20+ games, or almost a month to make up 6 games.
I know. I know. You can look through 125 of baseball history and find examples of whatever you want. So sure, you can lose a 6 game lead, in 6 games. But what is forgotten / ignored is that you are just as likely to turn a 6 game lead into a 12 game lead. But the above paragraph is more typical especially with no H2H. If the Nats take a 6+ lead after this series they should have a month sized cushion.
What will the dog days bring? A nice two months until the Mets try to mount a furious finish? A daily dogfight? This series helps set that up.