KILLINGTON, Vt. — The most enduring athletic careers are typically defined by a rivalry with an opponent of comparable talent or skill. Think Magic Johnson and Larry Bird, Tom Brady and Peyton Manning, Martina Navratilova and Chris Evert.

The American ski racing wunderkind Mikaela Shiffrin, who is on pace to break every prominent Alpine record, has never had a rival that has consistently challenged or exceeded her.

She does now. And the test to Shiffrin’s dominance has helped inspire her best skiing in two years.

On Sunday, Petra Vlhova of Slovakia, who is the sport’s reigning overall champion and who defeated Shiffrin in two of the first three races this season, once again led Shiffrin at the halfway mark of a race. But in a stirring comeback in the only women’s World Cup ski race on American soil this season, Shiffrin, competing an hour’s drive from her childhood home in New Hampshire, roared back with a blazing second run to win by a commanding 75-hundredths of a second.

“I feel more like myself; I don’t know that I can ski slalom faster than that,” said Shiffrin, 26, who tied the career record for World Cup wins in a single discipline with her 46th victory in slalom. Ingemar Stenmark of Sweden, skiing in the 1970s and 1980s, won 46 giant slalom races.

But the World Cup’s visit to the Killington ski resort also underscored the amplifying intensity of the Shiffrin-Vlhova rivalry as the attending fans, including a robust group that waved Slovakian flags and banners, clearly zeroed in on the head-to-head nature of the competition. In an interview on Friday from her Killington lodging, Shiffrin anticipated as much, saying that her friends and family have been wrapped up in the drama.

“They say it to my face — ‘wow, it’s so exciting,’” Shiffrin said with a laugh. “Even other athletes are sticking around to the end of races to see what happens. Overall, it’s pretty cool and a good thing for the sport. It certainly pushes me.”

Vlhova, who is also 26 but three months younger than Shiffrin, nodded in agreement after Sunday’s race when asked if she was aware of the focus generated by her battles with Shiffrin.

“Yes, of course, but it’s not just about me and Mikaela — there are also other girls, and we still have many races ahead,” she said. Vlhova then held up her left hand in a “let’s pump the brakes” gesture and added: “Just keep calm.”

But in a sport with fields as deep as 60 racers, this season’s results highlight the closeness of the contest between the top two ranked women’s skiers who have regularly separated themselves from their colleagues. Shiffrin has won twice and been second twice. Vlhova has won twice and finished second and third.

Despite being the same age, the two racers have not always been close rivals. Shiffrin was competing on the World Cup circuit when she was 15 and won her first race on it in 2012. She now has 71 World Cup victories, a career total that has been topped only by Lindsey Vonn’s 82 wins and Stenmark’s 86. Shiffrin has won three Olympic medals, including two gold medals. Vlhova won the first of her 22 World Cup races in 2015 and has not won an Olympic medal.

But in the last two seasons, Vlhova has eight World Cup victories to Shiffrin’s five. Shiffrin also missed months of the World Cup season in 2020 after her father, Jeff, died in an accident at the family home in Colorado on Feb. 2 that year. After the pandemic delayed or canceled most of her off-season training later in 2020, a still-grieving Shiffrin returned to racing and remained among the World Cup elite, but she did not thoroughly dominate as she once did. In the 2018-19 season, for example, she won an astounding 17 times.

On Friday, when asked to describe her relationship with Vlhova, Shiffrin also cautioned that the World Cup field was filled with many accomplished, fast skiers, but she said that when Vlhova was at her best “there’s not a whole lot I can do that’s better than what she’s doing.”

She added: “And when I ski my best, there’s not a whole lot that she or anyone else could do that is really better, either. But it’s all at a very high level, and it makes it more nerve-racking.”

Shiffrin and Vlhova have been clearly amiable after their four close races this year when they’ve hugged, chatted and congratulated each other. Before Sunday’s event, they did their prerace course inspection side-by-side and stood no more than six feet apart.

Still, Shiffrin conceded that being in close quarters with her week after week, including during the tense minutes in the cramped start area before a race, can be unnerving.

“Sometimes it can get a little intense,” Shiffrin said on Friday. “At the start of the season, we’re excited to get started, and it’s very positive.”

She laughed.

“But as the season goes on, you get a little more tired, and you’re pushing every single day and every weekend. You keep pushing the intensity level, and that other person, and it seems like it’s always Petra, is there.

“I’m just like, ‘Can we just call a truce for a second, just throw up the white flag just for one minute, and let’s both just take a really good nap?’ And then let’s get back to it.

“Every now and then you want to say that.”

It did not stop Shiffrin, who is notably gracious to competitors even in defeat, from complimenting Vlhova, who changed coaches after last season.

“She looks right now like she’s very solid on her shoulders and not only with her skiing technique,” Shiffrin said. “Her team this year, the atmosphere they have going on, seems a lot more positive. It’s always hard to know what other people are doing or did in the past, but there seems to be a bit more smiling going on than I’ve seen the past.”

On Sunday, Shiffrin trailed Vlhova after the first run by two-tenths of a second. Skiing second-to-last in the second run, Shiffrin made a significant mistake near the top and nearly skied off course, but corrected herself and increased her speed thereafter, charging through the final 40 gates to not only make up the first-run deficit against Vlhova but to gain a sizable lead.

Skiing last, Vlhova stumbled when her ski tips almost crossed after about 10 gates. She made a nifty recovery but lost valuable momentum and appeared to lose her rhythm within the course. Or as she said afterward: “I don’t know exactly what happened. I lost balance with both skis and then I went almost out. I tried to push as much as I could.”

She shrugged and grinned.

“I am happy with second,” she said.

Shiffrin has now won the slalom portion of the Killington event in each of the five times it has been held since 2016. Because of the pandemic, the races were not contested last year. A giant slalom scheduled for Saturday at the resort was canceled because of gusting winds and a heavy snowfall.

“I’m taking a lot of momentum from today and I feel I’m building on something now,” Shiffrin, who now has a narrow 20-point lead over Vlhova in the World Cup overall standings, said late Sunday afternoon. “When I compare this season to last season, I see so much more energy. I made a mistake in the second run, but I came back. For me, it’s a good sign.”