ATLANTA >> A final day that wasn’t on the schedule and won’t soon be forgotten.

An improbable comeback by the New York Mets in the opening game of a makeup doubleheader to secure their playoff berth. A gritty recovery by the Atlanta Braves in the nightcap, stamping their postseason ticket, as well.

And all the Arizona Diamondbacks could do was watch hopelessly from the desert, their hopes snuffed out by two games on the other side of the country.

“You’re just focused on getting into the postseason,” said Braves first baseman Matt Olson, soaked in champagne as he celebrated a 3-0 win in the last game of the regular season. “Whatever it took. If we had to play four games today, we would have done it.”

The regular season went to extra innings after the Mets and Braves had a pair of games rained out last week by Hurricane Helene. They controlled their own fates, with each holding a tiebreaker edge over the defending NL champion Diamondbacks.

Arizona needed one team to sweep, so they were pulling for the Mets after they overcame deficits of 3-0 in the eighth inning and 7-6 in the ninth to win the opener, going ahead for good on Francisco Lindor’s two-run homer.

“That was one of the craziest games I’ve ever been a part of,” said Carlos Mendoza, the Mets rookie manager. “Just the meaning of it. Coming back in the game and then losing the lead and then coming back again in the ninth. It was unbelievable, like you should write a book.”

The Braves, to their credit, bounced back to get the win they had to have. Even after ace Chris Sale was scratched because of back spasms, journeyman Grant Holmes stepped in to lead off a three-hitter spread among six pitchers.

At the end, in the perfect capper to a wacky day, there were champagne-spraying celebrations in both clubhouses at Truist Park.

Holmes found out he was starting about a half-hour before the first pitch.

“I was about to go get some food,” he said. “They came up to me and said, ‘Hey, you’re going to start this one off today.’ And I was like, ‘Oh, OK, here we go.’”

With their postseason berth locked up, the Mets added left-hander Joey Lucchesi to the roster to start the second game.