DALLAS — The look of bewilderment was common across the many sets of eyes throughout American Airlines Center on Thursday night, starting with Klay Thompson.

The Dallas Mavericks’ new addition was so shocked he was left so wide open for a fourth-quarter triple, he took a rhythm dribble just to set his body squarely at the rim.

Before the ball left his hands, the man who delivered the pass, Luka Dončić, was already headed downcourt, almost as if to say: “You let me have this guy on my team?”

That look was echoed by San Antonio Spurs second-year phenom Victor Wembanyama, who was stunned by the extra attention he received, with hands swiping at him and bodies thrown at him.

Wembanyama’s coming-out party was delayed by the reminder Thompson is arguably one of the five best shooters in NBA history, and the Mavericks are the Western Conference champions, with no plans to relinquish the title just because the conference got beefier at the top.

Dončić shook off summer rust, and Thompson showed none as the Mavericks showed no mercy on the Spurs on Thursday night. Thompson’s six triples were a team record in a player’s debut, as he scored 22 in Dallas’ 120-109 win.

Wembanyama’s second half of his rookie year already has many cementing his name as Defensive Player of the Year now and an MVP in the not too distant future. But he was given some rude treatment by draftmate Dereck Lively II and Daniel Gafford, the men who manned the middle during Dallas’ run to the NBA Finals.

Wembanyama’s final numbers looked effective enough, with 17 points and nine rebounds, but he found unexpected difficulty in getting looks, missing 13 of his 18 shots. The addition of veteran Chris Paul didn’t look too promising either, and it’s easy to surmise Wembanyama’s rough night combined with Paul’s debut in a Spurs uniform as correlated struggles.

But the night was more about Dallas, a team treated like an afterthought in a way despite its run through the spring. Minnesota is a trendy pick to make it to the Finals, but certainly not trendier than the Oklahoma City Thunder — who had the best record in the conference last season.

The Denver Nuggets actually won the NBA title in 2023, and there’s always discussion about the big box franchises in Los Angeles and the Bay Area.

Belief in Dallas is being whispered, not proclaimed with a bullhorn. Thompson’s finish in Golden State — a proud veteran unable to find a place with the only franchise he’s ever known — soured some folks on him through the summer.

But through the muck of free-agent negotiations, it’s worth noting he shot 39% from 3-point range last season and was at 41% following the All-Star break. He probably can’t be who he was, as he’ll turn 35 before All-Star Weekend this season, but he can still be impactful.

And playing next to Dončić, the NBA’s premier perimeter scorer, means great looks will be easy to come by — like that too-good-to-be-true triple one minute into the fourth. That rhythm dribble is because he has a tendency to overthink, but here he can catch and let it fly.

“It doesn’t make any sense because what we were taught growing up as far as being the best basketball players, you got to jump the highest, you got to run the fastest,” Thompson said. “But somehow, Luka defies that. He plays at his own speed and manipulates the game as good as I’ve ever seen anyone do it.

“It’s great to be a recipient of that.”

Thompson added he was just grateful for the make so it would make Dončić “not look stupid,” but that would be difficult on this night or any night.

There’s only so much space in the halfcourt, but playing with Dončić and Kyrie Irving — a supreme creator in his own right — means the real estate will be as plentiful as possible because those two must be monitored at all times.

“Klay’s being patient, we’re trying to figure out his spots,” Mavericks head coach Jason Kidd said. “When Klay is not shooting it, he can put it on the floor and make decisions. We talked about this in the past. When we get newcomers, our job is to hopefully get their feet settled. And I think you can see his feet are settled, and he’s comfortable here and he’s enjoying it.”

It’s the emotion of the first game, and it’s the Spurs who are far from championship vintage. There will be nights when Thompson struggles, where his feet don’t move on defense as well as they once used to — but this trio seems to function quite well on offense because even if he’s off, he cannot be left open.

“Like I say, it’s a lot of space for me and Kai [Irving] — not just for Klay but for everybody,” Dončić said. “You can’t leave Klay open. You can’t leave Kai open. So it’s … it’s going to be tough for the defenses, but we just got to go game by game.”

Dončić wasn’t his usual self in the first half, but once he put on a burst, the game was put out of reach midway through the fourth quarter, with the MVP chants a great accompaniment to his 28-point, 10-rebound, eight-assist night.

Irving and Lively scored 15 each, with Lively adding 11 rebounds and six assists.

It wasn’t lost on Thompson that he’s playing with Irving, whom he battled against during numerous NBA Finals in those Warriors-Cavaliers tilts, and Spurs forward Harrison Barnes is someone he won a title with during that first Warriors run.

It shows nothing lasts forever and the only consistency is change — so being pliable is the best attribute. It’s not that last season in Golden State didn’t leave a mark, or that this year will be smooth sailing.

It just means things are different.

“It makes you grateful to be in the NBA,” Thompson said. “You look around, you see those guys you came in with still playing at a high level, especially playing as Chris Paul [is]. I mean talking to CP now I’m like, ‘Man, I used to chase you around for 40 minutes.’ I used to hate his guts, now we’re good friends.”

Thompson’s off to play another good friend, Kevin Durant with the Phoenix Suns, in a couple of days after a great first night with many more tests on the horizon.