TALLAHASSEE, FL - JANUARY 12: RJ Barrett #5 of the...

TALLAHASSEE, FL - JANUARY 12: RJ Barrett #5 of the Duke Blue Devils dribbles with the ball against the Florida State Seminoles during the second half at Donald L. Tucker Center on January 12, 2019 in Tallahassee, Florida. (Photo by Michael Reaves/Getty Images) Credit: Getty Images/Michael Reaves

LAS VEGAS — While the debut of Zion Williamson was expected to shake up the NBA, he wasn’t even on the floor when it actually began to shake at Thomas and Mack Center.

With 7:53 remaining in Friday night’s NBA Summer League game between the Knicks and the Pelicans, an earthquake struck, sending the scoreboard swinging over the court and swaying the stands as the crowd rushed for the exits. The teams were escorted off the court for a delay as the public address announcer implored the crowd to remain calm and maintained that their seats were the safest place to be — a message that seemed to fall on deaf ears. The NBA canceled the game.

It was only a Summer League game, but even before the earthquake, it seemed like something far more.

The capacity crowd was on its feet, cheering wildly after every pregame dunk, recording every moment of the warmups. NBA stars sauntered out of the steamy heat outside and into courtside seats.

With No. 1 overall pick Williamson making his NBA Summer League debut and doing it against college teammate and friend RJ Barrett, the No. 3 pick in the draft, it just added to the allure.

New Knick Julius Randle was on hand. LeBron James was a spectator, joined by his still unofficial teammate, Anthony Davis. Lonzo and LaMelo Ball were in the house, along with DeMar DeRozen. Floyd Mayweather arrived with an entourage as large as most NBA rosters.

The front row of the arena included Knicks coach David Fizdale sitting with Garden chairman James Dolan, team president Steve Mills and general manager Scott Perry.

New York Knicks NBA basketball draft pick RJ Barrett speaks...

New York Knicks NBA basketball draft pick RJ Barrett speaks to reporters during a news conference, Friday, June 21, 2019, at Madison Square Garden. Credit: AP/Mary Altaffer

And even if the players were rookies making their first tentative steps into the league, the show quickly lived up to the hype. While tentative likely won’t be used to describe Williamson often, he began slowly on this night before beginning to take over. He dunked twice in a row, then swatted Kadeem Allen’s layup and was called for goaltending.

Just over seven minutes into the game, after a missed shot by the Pelicans, Kevin Knox grabbed a rebound, soaring above the crowd. Knox, who points to his time in the weight room as his biggest improvement heading into his second season, had a firm two-handed grip on the ball. Williamson reached in, grabbed the ball, yanked it — and Knox, who went tumbling to the floor — and turned and dunked it.

Williamson took a knee-to-knee hit late in the first half and left with soreness in his left knee. He did not return.

Zion Williamson, left, and the Knicks' Kadeem Allen chase after...

Zion Williamson, left, and the Knicks' Kadeem Allen chase after a loose ball during the NBA Summer League opener on Friday, July 5, 2019, in Las Vegas.  Credit: AP/Steve Marcus

Williamson and Barrett have taken to their new homes, and the NBA Summer League schedule-maker provided this stage for the first meeting — a sellout crowd of 17,500, with tickets reportedly going for as much as $400 on the secondary market and the game televised as the showcase of ESPN’s opening night coverage in prime time.

Barrett has spent the last five years playing on teams that were stocked with talent. At Montverde Academy, he said there were six players who now either are in or bound for the NBA. His one year at Duke included not only Williamson but Cam Reddish, who went 10th overall to the Hawks.

“I just feel like we are on TV every game,” Barrett said last month. “Everybody was watching us. Everybody knew who we were. Just playing at Duke itself, I’m just ready for everything. I love the biggest stage and I love the challenge.”

As the trio of Duke stars jockeyed for draft positioning, Barrett insisted there was no jealousy among the trio, no fighting over roles. “It was the best year of my life basketball-wise,” said Barrett, who scored 10 points and was 4-for-18 in his Summer League debut, including 1-for-8 from three-point range. “To play with [Williamson] and with Cam, those guys are such great guys. They’re better people than they are basketball players. We just had a great relationship. When my brother is doing great, why am I going to be jealous? Why am I going to be mad? There was no need. Everybody is trying to sit here like I wasn’t killing. We both did well. I’m just happy the team was winning.”

While they remain friends, they now are on opposite sides as competitors — for this night and in the long run for the Rookie of the Year award.

Zion Williamson, left, and the Knicks' Kadeem Allen chase after...

Zion Williamson, left, and the Knicks' Kadeem Allen chase after a loose ball during the NBA Summer League opener on Friday, July 5, 2019, in Las Vegas.  Credit: AP/Steve Marcus

“I’m not going to say that I don’t want it,” Barrett said. “I’m definitely going for Rookie of the Year for sure, it’s going to be a battle. But I’m confident enough that I can get it.”

Knicks Summer League coach Jud Buechler said of Barrett, “There were ups and downs in the game for him, which you expect out of a rookie. We saw a lot of things we liked. We will continue to encourage him to keep shooting and aren’t worried about his shot not falling tonight.’’

Notes & quotes: Mitchell Robinson was chosen for the Select Team that will play with Team USA under Gregg Popovich . . .Henry Ellenson left the Knicks’ Summer League team for personal reasons . . . Knox on the earthquake: “I didn’t feel it. I just saw people walking away and stuff, so I got off the court. I wasn’t scared. I just saw stuff shaking.’’