Jeff Hornacek was so hush-hush before his Knicks interview Monday with Phil Jackson, he refused to tell his mother or brother.

“He told us he had an interview with a team but couldn’t tell her who it was with — it was a secret,” his brother, John Hornacek, told The Post by phone Thursday.

John Hornacek owns a golf retail shop in Scottsdale, Ariz., and attended many of the Suns games his brother coached for 2 ½ seasons in which Jeff Hornacek recorded a 101-112 mark.

Hornacek was fired in February after a 14-35 start amid a bevy of injuries and reports his players had stopped responding. John Hornacek said he believes the Suns not giving his brother a contract extension cost him.

“You have a lame-duck coach, last year of his contract and they didn’t extend him,” John said. “I don’t know a lot of players who are going to respond to that.

“I know the way it ended, he was upset — not upset but angry. He still believes in the players and thought they could’ve finished better. He wanted to finish the job.”

Now, Jeff Hornacek is on the cusp of getting a second chance with the Knicks. In his first season as an NBA coach in 2013-14, Hornacek finished runner-up to Gregg Popovich for Coach of the Year. His brother said the Suns’ “up-tempo style took teams by surprise.”

“He wants to prove he’s a good coach, that Phoenix ending was just a fluke,” John said. “He’s got pride, but not an egotistical guy whatsoever. He wants to prove he’s a good coach.”

Hornacek, who played most of his career in Utah and Phoenix as a deft-shooting guard, has a lot of challenges ahead, including adapting to the negative New York pressure-cooker.

“I think with his demeanor, he’s pretty laid-back personality-wise,” John said. “Nothing bothers him a lot. It makes him a good coach — not a lot of highs and lows, but pretty intense, fiery guy. He’s a players’ coach, loves the players. In practices, he’s shooting with the players.”

It appears Hornacek will not be bound to strictly playing the slower-paced triangle offense — just pieces of it.

“Jeff plays an up-tempo style, but everyone has to have halfcourt sets,” John said. “I would think one thing about him, he’s up for anything, not a set-in-stone kind of guy. He adheres to the players. The triangle offense works good when you have guys named Jordan and Kobe. But Jeff respects the triangle. It’s won titles.”

John sees what Jackson likes in his brother.

“Jackson and Jerry Sloan had a lot of respect for each other,” John said. “They’re from the same mold, hard-nosed, tough. Jeff is a Sloan disciple.”

John hasn’t so much as visited New York City.

“I can’t wait. We’re from Chicago, so we’re used to the weather,” said John, who has two other brothers. “Everyone talks about how passionate the fans are.”