HOUSTON — In the latest grisly injury to afflict the Mets, Wilmer Flores left in the fourth inning of Saturday night’s 4-1 Game 2 loss to the Astros with what was diagnosed as a broken nose, suffered when he fouled a ball directly into his face. “I’ve had seven of them,” Terry Collins said. “They hurt.”

Blood gushed immediately as Flores doubled over in pain, the enduring image of a loss that completed Houston’s twinbill sweep. It’s unclear how much time he will miss. He’s scheduled for follow-up exams.

Seth Lugo (5-4) tossed five scoreless innings before being charged with four runs in the sixth, when he allowed the first four batters to reach base. The Mets (58-77) fell 19 games under .500 for the first time since Sept. 15, 2009.

Aoki added

In need of another outfielder, the Mets signed Norichika Aoki before the doubleheader. He started the second game in rightfield and went 1-for-5 with an infield single.

Aoki, 35, began play hitting .274 with five homers and 27 RBIs. He was released by the Blue Jays after beginning the season with the Astros. He worked out at a local park near his apartment in Toronto, and the Mets were the first team to express interest after his release. “It was kind of tough staying in shape,” Aoki said through an interpreter.

Aoki is arbitration-eligible next season, meaning the Mets could retain him past this month. That would require a salary above the $5.5 million he made this year, making it likely he will be non-tendered.

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Well-armed

Jamie Callahan and Jacob Rhame, the hard-throwing relievers recently acquired by the Mets in trades, made their big-league debuts in Game 1 of the doubleheader. “Good arms,” Collins said. “They’ve got legitimate good arms.”

Acquired from the Dodgers in a deal for Curtis Granderson, Rhame tossed 1 1⁄3 scoreless innings and hit 95 mph on the radar gun. “I’ve been wanting that since I was a kid,” he said.

Callahan allowed two runs (one earned) in two-thirds of an inning. He arrived from the Red Sox as part of the package the Mets received for reliever Addison Reed.

“It was the greatest thing ever,” said Callahan, who reached 96 mph. “The adrenaline was kicking in. I was just trying to soak it all up.”

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Extra bases

In his first game action since suffering a lat tear in April, Noah Syndergaard allowed two unearned runs in one inning in a rehab appearance in the rookie-level Gulf Coast League. He allowed two hits and struck out two. Said assistant general manager John Ricco: “The next step will be to keep ramping him up, probably throw two innings his next time out.” . . . Tomas Nido may be considered for a September call-up, which would give the Mets a third catcher. Nido, 23, is playing for Double-A Binghamton . . . The Mets confirmed that David Wright has been seen by doctors, though the club did not furnish a detailed update. Wright’s latest rehab assignment was shut down because of shoulder pain . . . T.J. Rivera has yet to decide whether he’ll have surgery to repair a partially torn elbow ligament.