HOUSTON — At this point Joe Girardi might want to...

HOUSTON — If the definition of insanity truly is doing the same thing over and over again and expecting a different result, then what do we make of the Yankees’ decision to play against Dallas Keuchel on Friday night?

They could have forfeited and saved themselves the trouble, right?

If you don’t feel like consulting your dictionary or rule book, let’s agree on something that requires no such diligence:

Dallas Keuchel has become the Yankees’ No. 1 nemesis.

This American League Championship Series kicked off as déjà vu to the 2015 AL wild-card game and didn’t look dramatically different from any of the regular-season instances in which Keuchel has faced the Yankees. The Astros captured Game 1 over the Yankees 2-1 because Keuchel once again dominated them and Masahiro Tanaka once again pitched admirably yet couldn’t match his counterpart.

The heavily bearded lefty accomplished what the more modestly bearded Corey Kluber could not do in the last round: He lived up to the hype.

“The Yankees are so storied,” said Keuchel, who threw seven shutout innings and allowed four hits and a walk while striking out 10 on 109 pitches. “It’s just a storied franchise, and they have so much rich history that you almost don’t even have to get up for the game. You’re already up for it. That’s what they bring.”

What Keuchel brings when he faces the Yankees is remarkable. For his career, in eight starts against the Yankees, including two postseason efforts, he owns a microscopic 1.09 ERA in 58 ²/₃ innings, with 62 strikeouts and eight walks.

“It’s who he is,” Joe Girardi said. “He’s a very good pitcher.”

Indians ace Kluber owned the Yankees for a long time, too, and he loomed large at the outset of the AL Division Series. Instead, the Yankees knocked around Kluber, the likely 2017 AL Cy Young Award winner, for nine runs in 6 ¹/₃ innings over two starts, including three runs over 3 ²/₃ innings in Wednesday night’s loser-goes-home Game 5.

The Yankees experienced no such turn of fortune with Keuchel, as their three-game winning streak came to a quiet conclusion. It didn’t matter the Yankees’ lineup featured only three players (lefty swingers Brett Gardner, Didi Gregorius and Greg Bird) from their 2015 AL wild-card loss at Yankee Stadium, in which Keuchel tossed six shutout frames and Tanaka gave up two runs in five innings for an eventual 3-0 Yankees loss. Keuchel muzzled and baffled these guys all the same, mixing his fastball, cutter and slider to keep the Yankees perpetually off balance.

“He was so good tonight and locked in mentally. He didn’t give in at all,” Astros manager A.J. Hinch said. “He was very convicted in his game plan. He controlled the bottom part of the strike zone. He even climbed a couple times. …

“[He] got a little bit of defensive help on some big plays and just continued to go out and got stronger as the game went on, which is an impressive characteristic when a starting pitcher can finish an outing the way that he did at a relatively high pitch count at this time of year.”

The defense did help, particularly left fielder Marwin Gonzalez’s fifth-inning bullet to nail Bird at home as he tried to score from second base on Aaron Judge’s two-out single.

Girardi said: “I thought our at-bats were much better against him the second time through the lineup.”

True, although that added up to little, and Bird’s two-out, ninth-inning solo homer against closer Ken Giles avoided the shutout while accomplishing little else.

“This was supposed to be the bridge year for them and they weren’t supposed to be here,” Keuchel said accurately of his opponent. “But they are here because they are good. And they are the Yankees.”

If his admiration for his foes transferred into anxiety, the Yankees would be in far better shape. Instead, as long as they win one of the next three games, they’ll try to beat Keuchel again in Game 5 at Yankee Stadium. Crazy as it sounds, they’ll hope for a different result. They might not have a choice if they want to keep this magical season going.