Jacob deGrom of the Mets pitches during a game against...

Jacob deGrom of the Mets pitches during a game against the Miami Marlins at Marlins Park on Sept. 3, 2014 in Miami. Credit: Getty Images / Mike Ehrmann

By simply taking the mound Wednesday night against the Marlins, Mets rookie righthander Jacob deGrom entered uncharted territory. For the first time, he has reached the grueling final month of a big-league season, a rite of passage that the rookie has been eager to tackle.

He looked prepared.

In his first September start, an eventual 4-3 victory by the Mets, deGrom fought through spotty command to hold the Marlins to just one run in six innings. But more importantly, he showed no signs of fatigue.

"I want to prove that I can pitch this late in the season," deGrom said. "I've never thrown this many innings in my life."

DeGrom departed with a one-run lead thanks to a two-run shot into the upper deck by Kirk Nieuwenhuis in the fourth. DeGrom was in line for his eighth win of the season, which would have tied him with Arizona's Chase Anderson for the National League lead among rookies. But lefty Dario Alvarez, making his big-league debut, allowed the tying run to score in the seventh on a single by Christian Yelich.

Still, deGrom bolstered his case for NL Rookie of the Year. His 2.87 ERA ranks lowest among NL rookie starters with at least 70 innings pitched. His 1191/3 innings and 112 strikeouts leads all NL rookies.

"It would be a tremendous honor for the whole organization, the guys that helped this kid along the way," manager Terry Collins said.

With the score tied in the eighth, the Mets pushed ahead on a run-scoring double by Travis d'Arnaud. Later, rookie Dilson Herrera added an insurance run when he beat out a potential double-play ball, allowing Lucas Duda to score from third.

The rally began on a drag bunt by Matt den Dekker, one of his career-high three hits.

The insurance run proved important in the eighth when the scorching Giancarlo Stanton hit his third homer of the series. His line-drive solo shot to left was his 36th homer.

But closer Jenrry Mejia shut the door in the ninth to log his 23rd save, giving the Mets a victory on a night in which David Wright went 0-for-5 with four strikeouts.

While Stanton made things interesting in the eighth -- bringing his team to within one run -- he did little against deGrom. Though he singled in the first, he hit into a double play and struck out.

The only run off deGrom came in the third, when Casey McGehee legged out an infield single as Duda failed to catch a low throw at first base. Otherwise, deGrom worked his way out of jams, even though he constantly fell behind in the count.

"Definitely a struggle with command," deGrom said. "I had a lot of 3-2 counts. But I managed to get out of a couple of situations where it really could have been a big inning."

Instead, deGrom battled through with a fastball that registered in the mid-90s, just as it has most of the season. It was yet another encouraging sign for Collins, who regards the final month of a grueling season the litmus test for any promising young player.

With his minor league innings included, deGrom has racked up 1572/3 innings with perhaps four starts remaining. He should remain within his limit of roughly 185 innings, allowing him the chance to pitch until the Mets reach the finish line.

"You don't know what it's like until you live it," he said. "Once they learn how to do it, when it's time to win, they're going to be able to compete."

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