The series has swung both ways. Washington won the opener 7-6. The Mets answered with a 7-1 blowout: A.J. Ewing hit a go-ahead 3-run homer and Ronny Mauricio went deep from both sides of the plate for his first career multi-homer game. That was the Mets' 4th game with 6 or more runs in their last 5.
Washington came in off a solid week at Detroit, winning 3-1 and 4-2 in back-to-back games after getting hammered in the opener there. The pitching held up in those two. It didn't hold up against the Mets: 13 runs allowed across 2 games, and only 1 run of offense on Saturday. The Nats need Herz to get through the order once cleanly and the bullpen to keep this from turning into Saturday again.
The Mets' injured list is mostly arms: Christian Scott, Tylor Megill, Reed Garrett, Robert Stock and Daniel Duarte are all out, so their bullpen isn't deep either. If Manaea pitches like he did last time out against Texas (6 innings, 3 hits, 9 strikeouts), that depth barely matters. If he doesn't, the late innings belong to 2 thin bullpens.
Then there's the weather. The forecast is 62 degrees with heavy drizzle, a 39% chance of rain and 13 mph wind at Nationals Park, and cool, wet afternoons don't usually help the ball carry. The Mets can finish 75-87 and Washington can reach 77 wins. It isn't much, but it's the last baseball either team plays until spring.