NEW YORK — A year ago, no one could’ve pictured this. Yet here they were, Dallas Keuchel and the Houston Astros, soaking in champagne, merrily posing for a victory shot on the mound at Yankee Stadium.

After all that losing, this was one October win to remember.

Pitching on three days’ rest for the first time in his career, Keuchel baffled New York for six innings of three-hit ball. Colby Rasmus and Carlos Gomez homered, and the Astros beat the Yankees 3-0 Tuesday night in the American League wild-card game.

“Nobody really gave us anything at the start of the year. And I don’t think anybody gave us a shot at the end of the year,” said Keuchel, the AL’s only 20-game winner.

The orange-clad Astros, who secured their spot in this winner-take-all game on the last day of the regular season, advanced to the Division Series against the defending AL champion Royals starting Thursday night in Kansas City.

Aggressive from the start in their initial playoff appearance as an AL club — and first since being swept by the White Sox in the 2005 World Series — the Astros came out swinging against Masahiro Tanaka in front of a revved-up Bronx crowd.

Rasmus sent Tanaka’s first pitch of the second inning soaring into deep right field. Gomez, who only had five plate appearances after missing nearly two weeks with a strained chest muscle in mid-September, connected on the first offering of the fourth.

“That really settled me down, and that’s who we are,” Keuchel said. “We hit a lot of home runs, pitch well and play defense.”

AL hits leader Jose Altuve had an RBI single off All-Star reliever Dellin Betances in the seventh.

Reliever Tony Sipp walked one, and Will Harris and Luke Gregerson were each perfect for an inning to finish the three-hitter. The boos from the 50,113 stunned fans in the crowd grew with each out as Gregerson closed for a save.

The Astros raced to an area between first and second after Brian McCann grounded out to end it and jumped up and down in a big scrum. As he was coming off the field, Keuchel pumped his fists toward a group of cheering Astros supporters in orange shirts — a few in big black beards — behind the visiting dugout.

It was a celebration a few years in the making, a raucous 30-minute party in the visiting clubhouse that carried onto the field. The Astros had averaged 104 losses in their previous four seasons.

“Now we get to go to Kansas City. It’s going to be some grind-it-out baseball,” Rasmus said.