SAN FRANCISCO — Reputations tend to stick if they ring true and, for a while, Andrew Wiggins’s reputation in the N.B.A. was that he was a bust.

For years, the word on Wiggins, a former No. 1 pick, was that he was inconsistent. That he was bad at defense. That he didn’t care.

The Cleveland Cavaliers had drafted him first overall in 2014 but traded him to the Minnesota Timberwolves less than two months later. More than five seasons in Minnesota bore little fruit, and after the Timberwolves went to the playoffs only once during that period they sent Wiggins to Golden State.

His latest stop, though, has changed things for Wiggins. Wednesday night offered one more example of his progression.

Golden State made a statement in the opening game of the Western Conference finals, leading the Dallas Mavericks by 30 points in the fourth quarter and winning, 112-87. Golden State’s point total wasn’t exceptionally high, but its defense propelled its victory.

Wiggins was a big part of that. The Warriors asked Wiggins to be their primary defender on the All-Star guard Luka Doncic, and Wiggins made sure Doncic didn’t hurt Golden State in the way he had hurt the Mavericks’ previous playoff opponents.

“That’s why he was the No. 1 pick,” Golden State’s Klay Thompson said of Wiggins. “You can’t teach that athleticism. You can’t teach that length. You can’t teach his timing. I’m just happy the world is getting to see who he really is.”

Doncic finished the game with 20 points, only one more than Wiggins and only 2 of them after the first half. He also committed seven turnovers and had only four assists. Doncic suggested after the game that an achy shoulder had played a role in his performance, saying it was causing him pain when he shot the ball, but added that he would be fine with some treatment.

But part of Golden State’s plan was to wear him out, and it was Wiggins’s job to do it.

“He took the challenge, and Luka’s tough,” Warriors guard Stephen Curry said. “He still finds a way to control possessions. You’ve got to assume he’ll shoot a little bit better, but Wiggs was relentless. Every possession, he was out there on him. That’s all we really want. Even if Luka has his numbers, you just want to, at the end of the day, feel like he had to work for everything he got.”

On Most possessions, Wiggins would start guarding Doncic in the backcourt, not allowing him to easily bring the ball up the court. Asked after the game if that all-court effort had tired him out, Wiggins shrugged and offered a half smile.

“I feel like I’m still young,” said Wiggins, who is 27. “I don’t really get too tired. I’m locked in. I’m motivated. And when you see it work or I feel like it’s helping us play better, it just motivates me to do it more.”

Said Thompson: “He just doesn’t seem to get tired.”

Thompson appreciated the effort more than most: the way Wiggins has been playing, he said, took some pressure off him.

“I don’t have to check the best player every night again,” said Thompson, who was known for his defense before missing the past two seasons with leg injuries. “Especially after what I’ve been through, it’s a nice change of pace.”

The 87 points the Mavericks scored were the lowest opponent total against Golden State this postseason. The Warriors have held opponents below 100 points three other times during the playoffs this year; each time, they have won.

The Mavericks had great success from 3-point range in earlier rounds, but made only 3 of 19 3-pointers in the first quarter Wednesday, and finished the game 11 for 48 from behind the arc. Those misses came from throughout their roster — it wasn’t only Doncic who struggled offensively. But Doncic is the player who drives the Mavericks, so his struggles loom larger.

After the final buzzer, Doncic let out a long exhale as he walked through the tunnel toward the visiting locker room at Chase Center. He wore a T-shirt over his uniform because he hadn’t played the final five minutes; by then, the game was too far out of hand for playing him to be worth the risk. His face was marked by an inadvertent red scratch from Wiggins, several inches long, from the right side of his nose down his cheek.

The Mavericks have a habit of losing big and recovering. They lost to the Phoenix Suns by 30 points in Game 5 of the Western Conference semifinals before beating them by 27 in Game 6 and by 33 in Game 7. Several Mavericks players on Wednesday spoke after the game about expecting a much better performance from Doncic during Game 2 on Friday.

“We’re under no illusion we’ve figured anything out,” Golden State Coach Steve Kerr said.

What they have figured out, and are glad others are seeing now, is that Wiggins has tapped into a part of his potential that might have been dormant, or at least less obvious in previous seasons.

Thompson said being with Golden State has allowed Wiggins to be himself. Curry said he’s learning how to win.

“Wiggs is understanding the nuances of what winning basketball is and just how to key in on the little things in terms of consistent effort from the defense, taking those one-on-one challenges, being aggressive on the offensive end, using his athletic ability to get to the rim if he needs to, confidence shooting the 3; being comfortable in our offense,” Curry said. “So there’s a lot of different things that he’s understanding that this time, in terms of a playoff run, requires to win games and the joy that comes with it.”

Wiggins passed the credit for that right back to Curry, Thompson and Draymond Green, who all won three championships and went to five straight N.B.A. finals together.

“It helps me see a different side of the game,” Wiggins said. “Being here, the culture, the people, organization, most importantly, just being around winners.”

A winner was not a label attached to Wiggins much at the start of his career, but during these playoffs he has showed more and more that it fits.