“I had a lot of butterflies. I was very nervous,” said No. 1 pick Karl-Anthony Towns, who had 12 points, four assists and three rebounds for the Timberwolves in his NBA Summer League debut. (John Locher/AP)

“Electric environment” and “summer league basketball” are two phrases almost never used together. But Thomas & Mack Center offered an anomaly Friday evening in Las Vegas. A record-setting crowd of 12,422 filled the arena — so many people that the upper deck was opened for seating — to create an atmosphere more suited for the playoffs than an exhibition.

They were on hand to watch more than just the Minnesota Timberwolves and Los Angeles Lakers, two of the NBA’s worst teams last season, in their summer league opener, an 81-68 Timberwolves victory. They filled the stands to catch a first glimpse of the NBA’s future.

In one corner, there was Timberwolves center Karl-Anthony Towns, the gregarious and versatile No. 1 overall pick out of Kentucky tasked to join Andrew Wiggins and Zach LaVine to forge Minnesota’s latest — and most promising — rebuild after an NBA-low 16 wins last season.

In the other, there was Lakers point guard D’Angelo Russell, the silky smooth No. 2 selection out of Ohio State assigned to mesh with Kobe Bryant for at least a couple seasons before headlining the next era of Lakers basketball — unless the Lakers ditch the rebuilding plan and ship him off to expedite the process.

The two 19-year-old rookies weren’t the only young talents on the floor Friday. The contest featured seven first-round picks from the previous two drafts. Jordan Clarkson, a second-round pick by the Washington Wizards who was traded to the Lakers on draft night in 2014, was a first-team all-rookie performer last season and could wind up being the best of the bunch.

No. 2 overall pick D'Angelo Russell, right, finished with eight points, six assists and five rebounds. He said after the game that he “felt rusty.” (John Locher/AP)

But all eyes were on the top two picks making their professional debuts.

The setting wasn’t unfamiliar for Towns. He played at the same arena three years ago as a member of the Dominican Republic national team against an American squad that included LeBron James, Bryant and other heavyweights. But Towns looked out of sorts to start.

Twenty-one seconds into his debut he air-balled a three-pointer from the left wing. He may have been the top pick a couple weeks ago, but his anxiety was evident.

“I started out like any other rookie — I ain’t going to lie,” the 6-foot-11 Towns said. “I had a lot of butterflies. I was very nervous. My legs felt heavy. It’s your first game out in front of everyone. You’re just trying to change the tide of the organization, especially being the number one pick.”

Towns settled down and exhibited his tantalizing potential, most notably through his heralded unselfishness and court awareness. He commanded double- and triple-teams in the post against a solid front line featuring Julius Randle, last year’s seventh overall pick who played his first game since breaking his tibia in last season’s opener, and promising undrafted prospects Tarik Black and Robert Upshaw. Towns coolly surveyed the floor to find cutters and open teammates. He finished with 12 points on 4-for-10 shooting with four assists, three rebounds, four turnovers and nine fouls — 10, not six, earns disqualification in the summer league, where quarters also run two minutes shorter. He played 32 minutes.

“You know, despite the jitters, he handled himself great,” said Ryan Saunders, a Timberwolves assistant coach who served as head coach Friday. “His finishing, them trapping him in the post to start the game, that shows the incredible respect he’s already getting in his league.”

Russell, however, was the rookie of choice for much of the crowd, many of whom were clad in Lakers jerseys — Los Angeles is just a four-hour drive away. Like Towns, the 6-5 southpaw didn’t record a gaudy stat line — he had eight points on 3-for-8 shooting, with six assists and five rebounds. But he flaunted his rare feel for the game while sharing the back court with Clarkson, who poured in 23 points.

Russell’s night began with a trip to the free throw line, when a faint “M-V-P!” chant could be heard before he had scored a point. He illustrated his exceptional court vision and passing ability with a drop-off dish to Black, who completed the sequence with a layup. A minute later, Russell pulled up at the top of the key to splash a three-pointer. He did it all fluidly, effortlessly handling the basketball and controlling the offense, never hurried and always in control, though he insisted there was room for improvement.

“Honestly, I felt rusty personally,” Russell said. “I was just trying to break a sweat, get that first wind out, and then just execute the offense to perfection. We got a lot thrown at us at one time so really just trying to fit in and gain that chemistry as quick as possible.”

There will be plenty of time for that. Friday’s rousing show, an exciting peek into the future, did nothing to quell expectations.