I think the key is to win this Nats game (assuming it is played). Then they just need 1 win in Houston and one Brewers loss. Clearly the Brewers are no better at sweeping every series/winning every game they are supposed to on paper than the Phillies are.
But the thing is, the Cubs aren't actually horrible. They went .500 in August, are 16-11 since, and 37-29 in the second half. Phillies are 36-30. Of course the difference there is literally the head-to-head!
And I think Dusty is just blowing hot air. Ya really think he's gonna let those starters throw 100 pitches, for instance, or overwork his bullpen trying to win for "integrity."? But I'm sure they will be at full-strength in Game 1 and then the starters will still play Sunday.