It can be a scary, exciting thing, making the leap to the big leagues. The opponents are stronger, bigger; the pitches come faster, and with more precision. And, if you’re a guy like Matt Reynolds, you have to rely on decades of prior, lesser experience to help you play at the game’s highest level and stay there.

Unless, of course, you’re Matt Reynolds on Wednesday afternoon, when the career infielder found out he’d have no prior experience to rely on, and would make his first professional start in left field. And by “first” we mean first ever. Including the minors. Throw college in there, too, for good measure.

But of course, if there’s one thing that separates major-league players from the rest of the mere mortals (other than skill, obviously), it’s this: They rise to the occasion.

StorySyndergaard experiences elbow discomfortStoryCespedes has mild sprain in wrist

Reynolds, in his 18th big league game, navigated a wind-swept left field for six innings and, most impressively, hit the game-winning home run, his first in the majors, as the Mets outlasted their World Series rivals, the Kansas City Royals, 4-3, to complete a two-game sweep in the Citi Field matinee.

Tied at three in the sixth, Reynolds crushed an 0-and-1 fastball from Joakim Soria to right center for the final margin, making good on a spectacular day from Asdrubal Cabrera and a middling one from starter Noah Syndergaard. Cabrera, whose athletic slide was responsible for a run in the fourth, also hit a two-run shot in the fifth, for a short-lived 3-2 Mets lead.

Syndergaard, who struggled with some uncharacteristic wildness, allowed three runs on eight hits over six innings. He didn’t walk anyone, but issued two wild pitches, one of which led to a run. He struck out four and improved to 8-2 this season.

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Both teams traded blows until Reynolds’ backbreaker, starting with the Mets in the fourth inning. Cabrera and Yoenis Cespedes reached on a walk and a single to lead off the frame, but after Neil Walker popped out in foul territory and Wilmer Flores struck out, it looked like it was going to be yet another wasted effort. That is, until Cabrera made it count.

James Loney singled to left and Cabrera, taking off from second, looked dead to rights while barreling into home plate against Jarrod Dyson’s strong throw. But with Salvador Perez splayed and blocking the plate, Carbera was about to slide around Perez, avoiding the tag and snagging the plate with his trailing hand, giving the Mets the 1-0 lead.

It would be short-lived, though. With one out in the top of the fifth, Cheslor Cuthbert turned on a 90-mph changeup and drove it to deep left to tie it. Dyson singled in the next at-bat and was sacrificed over by Danny Duffy. He scored on Whit Merrifield’s single to right-center to give the Royals the lead.

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But Cabrera put the Mets up again with a single stroke, his two-run home run off starter Danny Duffy. The good vibes, though, didn’t last for long. Cespedes appeared to hurt his hand fouling off a ball in the next at-bat, and left the game for Alejandro De Aza in the top of the sixth. That’s also when Syndergaard started to lose control.

After two quick outs, Syndergaard gave up a double to Perez, who advanced on a wild pitch and scored on, essentially, an unlucky hop. Paulo Orlando served up Syndergaard’s 1-and-1 slider back up the middle, but though Walker was in position to make the play, the ball hit off the second base bag and took a wild hop to score Perez and tie the game at 3. Syndergaard then served up another wild pitch before finally settling down to get Cuthbert on a comebacker.