Max Scherzer is coming off a start in which he gave up a season-high four homers in what was an unfortunate model for much of his year.

The Mets right-hander has allowed 22 homers in 100 ²/₃ innings after just 13 all of last year in 145 ¹/₃ innings.

And the problem isn’t going away.

He’s been smacked around for nine homers in his previous four starts and 15 in his last nine — a stretch in which he had a 5.09 ERA.

Scherzer’s answer to fixing the problem sounds simple enough: “Execute better.”

But he knows his difficulties this season run deeper than that as he heads into Friday’s start against the Nationals at Citi Field, in what will be his final appearance before Tuesday’s trade deadline.

“One of the hallmarks of what I’ve been able to do for the past several years is that I’ve been consistent,’’ Scherzer said Thursday, when he turned 39.

“Right now, I’m not consistent,’’ he said. “I have a good start and then some really bad starts. I haven’t been able to get on a consistent roll where you know what I’m gonna do every time out. That’s something I’ve got to be better at.”

He’s running out of time for that to matter, with the Mets needing to decide their route for the rest of this season by Tuesday.

He insisted the deadline has no bearing on how he prepares for his next outing.

“I’ve just got to go out and pitch,’’ Scherzer said. “What else can I do?”

So far this season, he hasn’t had many answers.

Among the glaring differences this year compared to much of the rest of his career is the homer.

He’s allowed two homers per nine innings, double his career average.

Asked if that is a more frustrating way to struggle than simply getting knocked around, since a solid start can be derailed by one or two pitches, Scherzer said it wasn’t.

“It’s just the game letting you know they’ve got something on you and they’re able to take home run-type swings and you’re giving hitters opportunities to hit the ball out of the ballpark,’’ Scherzer said. “I’ve got to do a better job of not giving them that opportunity. I’ve got to execute better. I get it.”

While that’s been one of the aspects of his game he’s worked on between starts, Scherzer said his routine hasn’t changed much from when things are going well.

“You’re always working on your craft and execution of pitches and making sure you hit the right spot,’’ said Scherzer, who is also walking batters at a higher clip (2.5 per nine innings) than he has for most of his career. “That’s what you do every time.”

Most seasons, though, Scherzer has been able to get himself out of rough patches much faster than he’s been in this one.

“The game always finds a way to surprise you in ways you don’t expect,’’ Scherzer said of his lengthy slump this year. “The moment you think you have this game figured out, you don’t. There’s always ebbs and flows with a season and you try to find that consistency.’’