LOS ANGELES - The legend of Jacob deGrom began back in the spring of 2014. In those days, he worked in obscurity in the back row of the Mets' pregame stretching line, where even his flowing hair barely set him apart from the rest of the unknowns.

Since then, deGrom has won the NL Rookie of the Year award, struck out the side on 10 pitches in the All-Star Game and etched his name in the record book alongside Hall of Famer Tom Seaver's. He has become a bona fide ace.

But on Thursday night, deGrom has the chance to take himself to another level, a jump that can be achieved only by conquering the almost invincible. Game 5 of the National League Division Series has created one of the great pitching matchups in recent postseason history, with deGrom facing the Dodgers' Zack Greinke in a winner-take-all showdown.

"It's probably dead even, to be honest,'' Dodgers lefthander Clayton Kershaw said. "As good as Zack is and has been the whole year, deGrom has been the same. So there's really no home-field advantage when you're facing a guy like deGrom.''

In his first full big-league season, deGrom, 27, went 14-8 with a 2.54 ERA, distinguishing himself even on the youngest, most talented pitching staff in all of baseball. In a Game 1 victory, deGrom tossed seven shutout innings and recorded 13 strikeouts, equaling Seaver's Mets postseason record.

The higher the stakes, the higher his focus, or at least that has been deGrom's preferred methodology.

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"Once I get on the field, the nerves go away,'' he said on the eve of the biggest start of his career. "And it's the same game we've been playing all year. If I do give up a hit or something, so what? I've still got to go out there and compete.''

In Greinke, deGrom opposes a pitcher who has spent the season making history. The Mets barely touched him in Game 2, no different than anybody else.

Greinke went 19-3 with a 1.66 ERA, although even those numbers fall short of truly capturing his dominance. When measured by adjusted ERA, which factors in a pitcher's ballpark and current era, Greinke logged one of the top 15 seasons since 1901.

The Mets face a harsh reality: Vanquish Greinke or go home.

"This, to me, is gravy,'' Mets manager Terry Collins said. "We're going to go out and play real, real hard. But they can't take away what these guys accomplished all year long. You can't take that away from them, no matter if we lose tomorrow night or we come out on top.''

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With their season on the line, the Mets are pulling out the stops. In an about-face, Noah Syndergaard and Matt Harvey will be available in relief. Although Collins said neither would throw more than two innings, one of them could wind up in a pivotal spot. Neither has ever worked in relief for the Mets.

Syndergaard spent his Game 2 whizzing 101-mph fastballs past the Dodgers. But Collins hinted that the rookie could be used in the seventh or eighth. Game 3 starter Harvey also may be used, despite the Mets' meticulous efforts to manage his innings.

"I talked to him on the plane today, and he said he'd be ready,'' Collins said. "So, if we need him, he'll be out there.''

The Mets' bullpen machinations, however, won't matter much unless they get the kind of brilliance they've come to expect from deGrom. As the playoffs loomed, Collins knew whom he'd view as his ace.

Even the schedule seemed to cooperate. Had the Mets faced elimination in Game 4, deGrom would have started on short rest. Instead, the Mets turned to Long Island's Steven Matz, so deGrom will take the mound on five days' rest, which is how he made 15 of his 30 regular-season starts this year.

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"We just thought this guy was pitching best,'' Collins said. "So if anybody was going to pitch two games in the series for us, it would be Jacob deGrom.''