In December 2016, after Warriors guard Stephen Curry drained a corner three-pointer in New Orleans, turned toward the Pelicans’ bench and high-fived an opposing assistant coach, social media was abuzz with a singular question: What was that about?

“Obviously, I know him very well,” Curry later said of the man who congratulated him, New Orleans associate head coach Darren Erman. “He’s yelling out, ‘If he makes it, it’s a good shot. If he makes it, it’s a good shot,’ trying to encourage their defense. So, I wanted a little praise for that good shot.”

A Golden State assistant for all three of former head coach Mark Jackson’s seasons (2011-14), Erman introduced a defensive scheme that remains foundational to the team’s system. Now, as the Warriors prepare to face Erman’s Pelicans in the Western Conference semifinals, Golden State players — some of whom credit Erman for making them appreciate defense early in their careers — expect to see plenty of defensive wrinkles.

It is an intriguing subplot in a matchup riddled with personal connections. One of the NBA’s premier defensive gurus, Erman is uniquely qualified to devise a game plan built around quelling the league’s highest-scoring offense.

“I do think (New Orleans head coach Alvin Gentry) has a defensive mastermind with him in Darren Erman,” Draymond Green, who spent his first two NBA seasons working closely with Erman, said recently. “I mean, obviously he knows a lot of us, coached us early on in our careers, but I know he’ll have some stuff up his sleeve.”

Erman is the rare NBA coach who didn’t play basketball in high school or college. After earning a math degree from Emory University in three years, he attended Northwestern University’s Pritzker School of Law and got a $150,000-a-year job at one of Chicago’s most prestigious law firms, Latham & Watkins.

A basketball junkie, Erman took a massive pay cut to become an assistant at St. Anthony High School in Jersey City, N.J., under renowned coach Bob Hurley. It was his work ethic and problem-solving abilities that, after low-level gigs at Brandeis University and with the Boston Celtics, landed him a player-development position in 2011 on Jackson’s Warriors staff.

Jackson was intent on getting Golden State, long one of the NBA’s worst defensive teams, to finally start caring about that side of the court. After the Warriors again finished toward the bottom of the league in defensive rating in 2011-12, Erman was asked to oversee the defense for Golden State’s summer-league team.

The Warriors had been running the “Show,” a pick-and-roll defense in which the defender guarding the screener briefly lunges at the ball above the level of the screen with his back to the sideline. Erman recognized that, as the NBA trended more toward small-ball, shooting-proficient lineups, the “Show” routinely left defenders out of position.

At the Las Vegas Summer League in July 2012, Erman installed the “Ice,” a side pick-and-roll defense in which the on-ball defender forces the ball-handler toward the sideline. Anchored by rookies Harrison Barnes, Festus Ezeli and Green, Golden State held opponents to an average of 63 points per game as it cruised to a 5-0 record.

Jackson was so impressed that he promoted Erman to a full-time assistant and told him to help lead the defense. Over the next two months, Erman put Green, Klay Thompson and others through 45-minute defensive boot camps every Monday through Thursday. Drills were geared toward everything from powering through screens to sliding their feet.

“Erm helped me a lot, especially the summer after my rookie year,” Thompson said of Erman, who declined to be quoted for this story. “He got into the gym, and while other guys were resting, he worked with me.”

To become a master of the “Ice,” Erman watched every defensive possession from Chicago’s previous two seasons. His former colleague in Boston, Tom Thibodeau, had enjoyed great success with the pick-and-roll defense as the Bulls’ head coach.

In 2012-13, their first season using the “Ice,” the Warriors’ defense vaulted from No. 27 in the 30-team NBA to No. 13. A year later, Golden State finished at No. 3.

In May 2014, when Steve Kerr replaced Jackson as the Warriors’ head coach, he realized that — for perhaps the first time in decades — the team’s offense needed more work than its defense. Though Golden State switches far more on pick-and-rolls than it did under Jackson, it still uses many of the same principles Erman introduced a half-decade ago.

In three seasons with New Orleans, Erman has brought a moribund defense respectability. His creative game-planning was on full display in the Pelicans’ first-round sweep of Portland. New Orleans smothered All-Star point guard Damian Lillard with multiple defenders, repeatedly forcing the Trail Blazers to rely on middling shooters to make jumpers.

“They were really good against Portland, and we’ve watched those games carefully to see how they attacked the Blazers,” Kerr said. “They had a hell of a series. I thought their staff did a really good job.”

The Warriors, who could have Curry (sprained left MCL) back as soon as Game 1 on Saturday, present considerably more headaches for a defensive coordinator than Portland. This time, if Curry drains a three-pointer in front of the Pelicans’ bench, Erman won’t be so apt to high-five his former pupil.

Connor Letourneau is a San Francisco Chronicle staff writer. Email: cletourneau@sfchronicle.com. Twitter: @Con_Chron