WHEN Sloane Stephens won the US Open, having been ranked world No.957 just two months earlier, she was hailed the new star of tennis, an ultra-talented fairytale who would be a force for years to come.

But since then? Disaster.

Stephens, 24, has lost every single match she has played since raising the trophy for her maiden Grand Slam title on Arthur Ashe Stadium, where she made history as the lowest-ranked player (No.83) to ever win the Open title. American hopes that should would follow in the footsteps of the Williams sisters as a dominant force in women’s tennis have dramatically been put on ice, for now.

“Considering how amazing she played at the Open and in the summer, it’s one of the strangest four months,” Brad Gilbert, the former pro and coach of Andre Agassi, told the Wall Street Journal. “It makes no sense.”

Women’s tennis legend Chris Evert, the 18-time Grand Slam champion turned ESPN commentator, had a damning take on Stephens’ downturn.

“I question whether she has a burning desire to win more Grand Slams or be No.1,” she told reporters. “I don’t see it as much as I do with other players.”

Yet Evert also cut Stephens some slack, saying her stunning rise to stardom brought with it some major changes to her career.

“I don’t know what’s going on with Sloane,” Evert said. “This is what happens to surprise winners; we’ve seen that. It changes your whole life. There’s more press, more appearances, she’s doing her charity work, plus she’s been injured. It’s taken a toll.”

Stephens made a high-profile sponsorship move from Under Armour to Nike earlier this month, joining Serena Williams, Roger Federer and Rafael Nadal in the Swoosh stable. But her first outing did not go to plan - at all.

After withdrawing from the Brisbane International due to a persistent knee problem, the world No.13 was just crushed 6-3 6-0 by No.100 Camila Giorgi in the first round of the Sydney International. It was her seventh consecutive defeat since beating Madison Keys by that exact scoreline in the US Open final last September.

After becoming a Grand Slam champion, she lost 6-2 6-2 to world No.55 Qiang Wang in Wuhan; 6-3 6-0 to qualifier and world No.73 Christina McHale in Beijing; 7-5 6-3 to world No.15 Anastasija Sevastova at the WTA Elite Trophy, before retiring from her second match against No.23 Barbora Strycova while down 5-0 (knee). She also lost two matches in the Fed Cup final, against world No.78 Aryna Sabalenka and No.87 Aliaksandra Sasnovich, both three-setters.

Sloane Stephens was a surprising and popular US Open winner. Source: AFP

While Stephens is renowned as a player who primarily relies on exceptional defensive tennis, the other side of her game waned further during this run, according to former Grand Slam champion Lindsay Davenport.

“Sloane’s offense doesn’t seem as turned on as it was this summer,” Davenport said on Tennis Channel. “Throughout the summer, she was doing such a great job of finishing points when she had the opportunity.”

Sloane Stephens at the Sydney International. Source: AAP

Stephens herself has played down her struggles, saying she did not expect them to linger this year.

“I think there were a few tournaments that I wasn’t ready to play mentally or physically and you’re never going to get a good result out of that,” Stephens said last month.

“But I didn’t lose any confidence from it. I’m going to go into 2018 super pumped and excited just the same.”

She also denied being overwhelmed by new demands on her time.

“I’m just kind of taking everything in stride … and making the most of my time,’’ she said.

“I don’t like to do a whole lot anyway, so I’ve been very low key and under the radar and just trying to live my normal life because that’s I think what works best for me. I just like to be very simple.”

Sloane Stephens during her heavy Sydney International defeat. Source: AFP

Stephens’ agent John Tobias said of her form slump: “I’m not concerned in the least.” Yet the US media has pounced on Stephens’ downturn, with Wall Street Journal reporter Tom Perrotta calling her run “one of the most disastrous encores to a major title in memory”.

Forbes’ Filip Bondy pointed out that: “Other winners of majors have also struggled in recent years to avoid a slump or maintain the No. 1 ranking. The women who captured majors yet then failed to dominate the sport include Angelique Kerber, Jelena Ostapenko, Petra Kvitova and Garbiñe Muguruza. There are other top-ranked women – such as Simona Halep, Karolina Pliskova and Caroline Wozniacki – who have never won even a single major.”

Sloane Stephens needs to arrest a form slump in 2018. Source: AAP

Writing for Tennis Magazine, Steve Tignor asked whether Stephens had fallen victim to a well-known sporting jinx.

“Sports Illustrated seemed to make her ascendancy official when it put Stephens on its cover, under the headline, SLOANE STEADY: Her Story Was Already Special. Now the Sloane Stephens Tennis Journey Has Substance. But SI has a well-earned reputation for jinxing its cover subjects, and it didn’t take long for Stephens to succumb,” Tignor wrote, adding that despite her unlimited potential, a quick turnaround for Stephens seemed unlikely.

“Her game is a delicate balancing act of consistency and aggression, of defense and offense, of knowing when to play it safe and when to pull the trigger. Like Angelique Kerber, also an athletic defender, Stephens needs to play lots of matches to find her groove. In 2017, we saw what happened to Kerber when she got off to a slow start and didn’t build any momentum— she dropped from No.1 to No.21. And we saw what happened to Stephens when she played match after match in the summer—she found the confidence to win the US Open.”

Sloane Stephens has had a tough start to 2018 in Australia. Source: AFP

Should Stephens’ slide continue, at least she knows the way back from oblivion to the top. Last year, amid an 11-month recovery from foot stress fractures that needed surgery, her ranking ballooned to No.957 in July before a run of form powered her back to No.83 - in just one month.

Stephens will face world No.35 Zhang Shuai in the first round of the Australian Open, boasting a 2-1 head-to-head edge over the Chinese player.

At any rate, she has already enjoyed lucrative success. She banked an incredible $US3.7 million for winning the US Open, the biggest winner’s cheque in women’s tennis history, while her career prizemoney earnings sit at $US8.3 million.