NEW YORK — When Jonah Tong fell behind in the count against his final batter, New York Mets catcher Luis Torrens twice pointed his mitt at the 22-year-old, firmly ordering a strong finish.

Five pitches later, Tong got San Diego Padres catcher Freddy Fermin to fly out to end the fifth inning.

In the Mets’ dugout, manager Carlos Mendoza considered leaving Tong in for the sixth inning despite reliever Tyler Rogers being warm in the bullpen. Perhaps if the Mets added to their lead in the bottom of the fifth inning, Tong would’ve stayed on the mound. They did not. Also, the Padres had the top of their order due up. More importantly, however, from Mendoza’s perspective, it was vital for Tong to finish the outing feeling good about his work.

“One hundred percent,” Mendoza said.

Last week, Tong raised questions about his readiness for the major leagues.

In the Mets’ 6-1 win over the Padres on Thursday, Tong introduced the idea that he can handle playoff innings.

Indeed, when it comes to the Mets this September, things can change fast. Their win ensured they’d finish Thursday two games ahead of the idle Arizona Diamondbacks for the final wild-card spot. Nine games remain.

Against the Padres, who hold a four-game lead over the Mets for the second wild-card spot, Tong tossed five innings, allowing one unearned run and four hits (no walks). He recorded eight strikeouts. The Padres manufactured the lone run in the fourth inning when Fernando Tatis Jr. hit a one-out single, moved to second base on an errant pickoff attempt, scooted to third base on a wild pitch and scored on a sacrifice fly. Luis Arraez’s fly ball traveled just 233 feet to left fielder Brandon Nimmo, who made a poor throw. Tong’s 82-pitch day gave the Mets what they needed.

The Mets’ rookie trio, Brandon Sproat, Nolan McLean and Tong, have now combined to throw 17 straight innings without allowing an earned run. If the Mets reach October, McLean looks like a definite playoff starter. Sproat, who makes his third start on Saturday, is resembling one, too. The other options? The Clay Holmes-Sean Manaea piggyback tandem looked good. David Peterson did not. And it remains possible Kodai Senga jumps back in the mix, but Mendoza was noncommittal about that idea heading into Senga’s scheduled start in Triple A on Thursday. So, count Tong as another viable option.

It did not look like that six days ago. Against the Texas Rangers, Tong recorded just two outs, allowing six runs, four hits and three walks in the first inning of the Mets’ 8-3 loss. Tong threw 40 pitches. The Rangers swung at just eight.

In his disastrous start against the Rangers, Tong conspicuously leaned heavily on his changeup. He kept falling behind in counts. Also, he dealt with an illness. While in Philadelphia, the Mets sent Tong back to the hotel twice. When he was at Citizens Bank Park one day for a bullpen session, he carried with him a tall cup of tea. Perhaps it was just an all-around rough week for Tong.

Afterward, several veterans, including Sean Manaea, Ryne Stanek and Nimmo talked with Tong about moving past the bad start. Tong said that a lot of times, players do not register everything their peers tell them after a game, but in this case, he absorbed much of the wisdom he heard. The simple gist was, everyone has gone through something similar at some point in the major leagues.

“I’ve had outings like that in the past,” Tong said. “It just takes a day to let it flush and get right back. I’m really grateful to have the support of the clubhouse. It definitely gave me confidence, for sure.”

Club officials said they sensed Tong had put the start (only his third since his callup) in his rearview mirror after one day. They liked his preparation and demeanor in the days leading up to Thursday.

Things could not have looked more different against the Padres. Tong bounced back in a major way.

Tong also brushed off a shaky first inning. After Arraez hit a one-out single, Manny Machado followed with a hard-hit ball to left field. Machado, however, tried to stretch the hit into a double, assuming Nimmo’s throw would go to third base. Instead, Nimmo hit cutoff man Francisco Lindor, who then nailed Machado at second base. Tong struck out the next batter, Jackson Merrill, to end the inning. From there, he was mostly rolling.

While rival scouts questioned Tong’s readiness last week, citing a need for a third pitch, people within the Mets believed he was just a couple of pitches away from potentially having a different kind of outing against the Rangers. Either way, Tong operated much differently against the Padres, a club that does not fare well against fastballs.

Tong threw his fastball 67 percent of the time, attacking with the pitch inside the strike zone. In the third inning, he struck out Machado using high heaters, the last one well out of the strike zone and timed at 95.6 mph. But Tong also used enough curveballs (18 percent) and changeups (12 percent) to keep the Padres honest.

“That was the guy we saw at the minor-league level pretty much the whole year,” Mendoza said. “It was pretty impressive.”

It was quite the turnaround for a rookie whose character often earns praise from inside the Mets.

“That shows a lot of character from him,” Nimmo said. “I couldn’t be more proud.”

After Tong on Thursday, Mendoza deployed his four best relievers for one inning each: Rogers, Brooks Raley, Gregory Soto and Edwin Díaz (in that order).

The combination of the pitching configuration with the lineup’s production (Pete Alonso hit a solo home run and Nimmo added a three-run home run) worked.

Perhaps it is a formula the Mets try in October?

(Photo: Ishika Samant / Getty Images)