Mets starting pitcher Chris Bassitt walks off the mound after...

Mets starting pitcher Chris Bassitt walks off the mound after being taking out of the game during the fourth inning against the Chicago Cubs in an MLB baseball game at Citi Field on Monday, Sept. 12, 2022. Credit: Kathleen Malone-Van Dyke

Well, they don’t call them the dog days of summer for nothing.

After two crackling offensive performances against the Marlins, the Mets folded against a thoroughly beatable team Monday night, managing almost nothing against a rookie making his fifth major-league appearance and losing to the Cubs, 5-2, at Citi Field.

What’s more, the offensive malaise had to be witnessed not only by the 29,081 fans on site but the few hundred dogs there for “Bark in the Park Night.’’

Chris Bassitt was hounded from the onset, allowing five earned runs in 3  2⁄3 innings, his second-shortest outing of 2022.

Down by four in the eighth, the Mets loaded the bases with none out when Jeff McNeil and Pete Alonso singled and Daniel Vogelbach walked, but Manuel Rodriguez struck out Mark Canha. Cubs manager David Ross brought in Brandon Hughes, who got Eduardo Escobar to fly out to center. Pinch hitter Darin Ruf flied out to shallow right to end the threat, even with the dogs chanting his name.

Buck Showalter opted to hit the slumping Ruf over rookie Mark Vientos, he said, because the Mets had lost the DH (Ruf took over duties in right in the ninth). He also said he preferred the veteran’s track record despite the fact that Ruf is 1-for-34 and a career .152 pinch hitter.

“It’s frustrating,” Ruf said. “I’m just trying to have good at-bats and sometimes you need a little luck.”

Francisco Lindor’s solo homer in the ninth provided the final margin.

The Mets (89-53) remained 1 1⁄2 games ahead of second-place Atlanta, which lost to the Giants, 3-2.

The Mets stranded seven runners against Javier Assad in his six innings, four of them in scoring position. They left 10 men on and were 1-for-9 with runners in scoring position.

That trend started early, with the Mets loading the bases with two outs in the first but failing to capitalize as Assad struck out Canha looking.

The Cubs (59-82) made the Mets pay for it. Rafael Ortega hit a solo shot with two outs in the second. Bassitt walked Alfonso Rivas to lead off the third and one out later, Zach McKinstry drove a sinker 423 feet to right to give the Cubs a 3-0 advantage.

Bassitt issued another leadoff walk in the fourth and again came to regret it. Ian Happ advanced to second when Alonso drew an error on a pickoff throw, reached third on a groundout and scored on Ortega’s single to left. Ortega scored on Rivas’ two-out single, ending Bassitt’s night.

“It was a bit of everything,” Bassitt said. “I wasn’t locating anything . . . Just a bad start.”

Bassitt, who leads the staff in innings pitched by a margin of 30 innings, allowed five runs and five hits with two walks and two strikeouts. It was only the third time in 27 starts in which he didn’t go at least five innings.

Assad, who boasts a devastating cutter and has allowed one run or fewer in four of his five major-league starts, didn’t crack until the fourth. He allowed one-out singles by Canha and Escobar, who extended his hitting streak to 10 games, and a two-out RBI single by James McCann. That cut the deficit to 5-1, but Assad struck out Brandon Nimmo swinging to strand two.

Assad allowed one run and five hits with three walks and six strikeouts in six innings and lowered his ERA to 2.53.

It was a less-than-ideal start to what is, on paper, an easy closing stretch for the Mets. They are just past the halfway point of 16 straight games against sub-.500 teams (they’re 5-5 thus far), and 14 of their remaining 20 games are against teams with losing records. That’s good enough for the second-easiest remaining schedule in baseball, according to Tankathon.

Not much they can do about anything but themselves, said Showalter, who added that he doesn’t even look at the standings if he can help it.

“You can’t get caught up in that world,” he said. “It requires some discipline because you do care a lot — don’t confuse it with that. It’s why we get up in the morning. But you realize what you can control and not.”

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