WASHINGTON — The Mets have lost four straight and five of six games. The offense that routinely turned all pitchers into mush suddenly is flawed.

What could be worse?

How about having that suddenly scuffling offense about to go up against Max Scherzer?

Yup, the former Cy Young winner, he of the two no-hitters in the same season and a 20-strikeout game in his last start, leads the Nationals’ pitching setup for the May showdown series with the Mets starting Tuesday at Citi Field.

“He’s an ace,” former Met Oliver Perez, now a Nationals reliever, said simply of Scherzer, who fired one of the greatest games ever Wednesday when he became the fourth pitcher to strike out 20 batters in nine innings — and he did it with 119 pitches, including 96 strikes.

“Let’s just say I’m happy that we had six days,” Scherzer said of his time off — including an off-day Monday — following his historic effort.

There hasn’t been much real rest for Scherzer. Just keeping up with text messages was exhausting. But some of it has been fun — like posing for pictures at the intersection of 20th and K Streets in Washington.

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“Lot of texts. Lot of people reaching out, congratulating me,” said Scherzer, who rated his 20-K effort as “kind of equal” to throwing two no-hitters last season — one of which came at the Mets’ expense in Scherzer’s final start of last season.

“They’re both impressive [feats],” Scherzer said. “Everybody enjoyed watching it.”

Yeah, the Tigers probably watch the film over and over. But leading the list of those who really appreciate the performance is Scherzer himself.

“You always want to sit there and beat yourself up and watch all the video in the world when you go out there and get lit up, but sometimes you have to appreciate what you did well,” Scherzer said. “Create that positive momentum for yourself. I can’t say I’m always going to pitch like that.

“But I have the ability to pitch extremely well and help the ball club win. That’s something that I can do, that’s what I expect out of myself every time I take the mound.”

The Mets can’t be overjoyed hearing all that. But Scherzer, who opposes Noah Syndergaard, for whom he had respectful praise, knows the Mets will be waiting, looking to bust out of their scuffling ways.

Teammates predicted the Mets would be ultra-aggressive against Scherzer, who chose to keep his expectations private.

“Rather not say. I have my ideas,” Scherzer said of what he expects from the Mets in terms of approach — although he spoke of what he expects from the Mets in general, which is a balanced offense.

“They’ve got right-handed, left-handed hitters. Both sides have power threats,” Scherzer said. “They’ve got some speed. … It’s a tough lineup to navigate because it’s long, it’s deep and you’ve got to execute all your pitches the entire night.”

Scherzer, like all returning Nationals, remembers how 2015 went to Hades. The team many picked to win it all unraveled in every way with the Mets aiding the demise.

“Yeah, that’s the team that beat us. Much respect to what they did last year and they get all the credit and deserve all the credit,” Scherzer said noting it is not so much a question of payback but pure competition. “It’s ‘Look we want to come in and beat you.’ Simple as that. We’re competitive. We know we’re a great team. Obviously we have a lot of respect and we think they’re a great team as well.

“You approach it the same way you approach every series: Try to go in there and win. That’s where you just try to keep it simple. Don’t try to make this complex and make the game somehow harder than it is. You just got to go out there and try to win the series, do everything you can to beat them.”

Simple. And you start by sending out a hands-down ace in the first game.