If everything had gone as the Mets planned this season, Rene Rivera wouldn’t have spent a day in the major leagues.

When the season started April 3, the Mets had two young catchers in Travis d’Arnaud and Kevin Plawecki. Rivera was sitting at home after getting released by Tampa Bay at the end of spring training.

After talking with Texas and St. Louis, Rivera signed a minor-league contract with the Mets on April 5. Three weeks later, he was in the majors after d’Arnaud went down with a rotator-cuff injury. Rivera made his Mets debut April 30.

D’Arnaud is back and healthy, but it will be Rivera behind the plate when Noah Syndergaard throws the first pitch of the National League wild-card game against the Giants Wednesday night at Citi Field.

“It’ll be awesome,” Rivera said. “It’ll be an awesome experience. I can’t wait.”

Syndergaard made 31 appearances (30 starts) and Rivera, 33, caught 23 of them. D’Arnaud and Plawecki caught four each. Syndergaard’s ERA, which was 2.60 overall, was 2.50 with Rivera versus 3.57 with d’Arnaud and 2.18 with Plawecki.

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“Noah is one of the best pitchers in the National League,” Rivera said. “You just have to keep it simple with him. You’ve got to be on the same page, and that’s what we’ve been doing all season. We know each other. We talk about how we’re going to approach things, how we feel that day. You have to communicate with the pitchers, and that’s what’s been so good with Noah.”

Rivera hit .222 with six home runs and 26 RBIs. It is his defensive prowess that will earn him the start in his first postseason game.

Syndergaard is not good at preventing stolen bases, as 48 of 57 potential base thieves were safe against him. The Giants were eighth in the National League with 79 stolen bases.

Rivera threw out 30 percent of would-be base-stealers this season. D’Arnaud threw out 22 percent. The NL average was 27 percent.

Rivera wouldn’t have been here at all if things had been different. But here he is.

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“In the catching position, I always say that you’re a foul tip away from being there,” he said. “Me and my agent, we talked about the opportunity to be in the big leagues. As a player, that’s what you want. When the interest was there, we felt like the opportunity was there. I took the chance to go to Triple-A for a little bit and things worked out good. I got the opportunity when d’Arnaud got hurt and I just came here to play my game.”