A manager spends a season building up trust, particularly with his best players. He will show faith during a slump, endure a bad week with the big picture in mind.

In the playoffs, though, all that matters is Here — and his brother Now. Small focus is vital when momentum sways magnificently with each outcome. One day you win the ALCS opener in Houston, improve to 4-0 in this postseason, feel like a team riding a magic carpet. Blink twice and the Yankees are now down two games to one to the Astros.

“You don’t make friends in the postseason,” Joe Torre told me Tuesday before ALCS Game 3. “You try to win the games.”

Torre managed the most games in playoff history (142), and in his first postseason with the Yankees he benched stalwarts Wade Boggs, Tino Martinez and Paul O’Neill for World Series Games 3-4 and all but O’Neill for Game 5 to play hotter hands in Cecil Fielder, Charlie Hayes and Darryl Strawberry, who all joined that season already in progress.

“Zim taught me that during the postseason you can have no patience,” Torre said of his then bench coach Don Zimmer.

Aaron Boone must lose patience now. After a 4-1 Game 3 loss Tuesday, however, Boone was still talking about pieces of at-bats being positive for Adam Ottavino and Gary Sanchez taking good swings without results. This didn’t sound like Torre in October, more like Mickey Callaway’s Pollyanna preambles of June.

The Yankees have lost two straight games and home-field advantage and they have not broken through against Justin Verlander or Gerrit Cole, a must if they are to win this series. They managed three runs in 20 innings in Games 2-3 started by Verlander/Cole.

The Yankees forced Cole to work Tuesday, but ultimately did not deliver a big blow. They were 0-for-6 with runners in scoring position in the righty’s seven shutout innings. After Jose Altuve homered as the second batter of the game, DJ LeMahieu and Aaron Judge opened the bottom of the first with singles and Gleyber Torres walked with two outs. No run was scored.

That inning essentially encapsulates the Yankees’ ALCS offense. LeMahieu, Judge and Torres are 14-for-38 with three homers, eight RBIs and five walks — Torres’ eighth-inning homer off Joe Smith accounting for the Yanks’ lone Game 3 run. Everyone else is 10-for-71 with two homers, two RBIs and six walks.

So Sanchez, who was 0-for-4 with two strikeouts, is not alone in offensive malfeasance. But October struggles are now part of his résumé: 1-for-13 with six whiffs in this ALCS, 2-for-25 with 12 strikeouts and no extra-base hits in these playoffs and 16-for-92 with 34 strikeouts in his postseason totality. Still, Boone said he would not sit Sanchez for Austin Romine.

“I’m seeing Gary miss some pitches,” Boone said. “I felt like he got another good one to hit today and put it on the net [behind home plate] again. He’s got to take advantage of — especially when you’re facing a team like this with pitching like they have, when you do get a ball that you can handle, you’ve got to make sure it gets in play with authority and not on the net.”

Sanchez has tended to lose confidence and concentration when he struggles on offense and it often turns to defensive problems. And he failed to block a Zack Britton run-scoring wild pitch in the seventh on which he did not move well. Boone said Sanchez has been “great defensively.” Sanchez insisted he has not lost confidence.

Ottavino said the same, that his belief in himself is as strong as ever. But he also said he has no answers why he is pitching so poorly.

Ottavino left a first-and-third mess for Britton in that seventh inning of a 2-0 game, walking George Springer and allowing an Altuve run-and-hit single to a vacated second base to put runners on the corners. They were the only two batters he faced. He has now allowed nine of the 16 men encountered this postseason to reach — and the tying homer he allowed to Springer in Game 2 is so far the biggest hit of this ALCS.

“I am consistently not getting the job done,” Ottavino said. “That is frustrating.”

The Yankee run prevention has been great aside from one pitcher — Ottavino has appeared in all six postseason games and has an 11.59 ERA. The other Yankee pitchers have a 1.88 ERA. “Everyone is throwing the ball well except for me,” Ottavino said. Yet, Boone insists he will stick with the righty, keeps saying they can’t get where they want without him.

That would be the Canyon of Heroes. But the Yanks have deviated from that path, in part because of Boone’s continued trust of this version of Ottavino. This isn’t May or June, with plenty of schedule left as an ally. It is October.

No time to make friends. No time for patience.