NEW YORK — When the U.S. Open’s attempts to seed Serena Williams fairly in her return from maternity leave ended up dropping the American into top-seeded Simona Halep’s quarter of the draw, the early talk of the tournament was how tough of a road Williams would have.

Williams, seeded No. 17, would have to play her sister Venus in the third round, fans lamented, and if she got through that then the reigning French Open champion Halep likely awaited two rounds later in the quarterfinals. Beyond that there was groaning that she could meet defending champion Sloane Stephens or even an old hard-court rival such as Victoria Azarenka in the semifinals.

Perhaps there is a reason most players don’t look too far ahead in the draw.

While Williams rocketed to victory in her 15th U.S. Open quarterfinal with a 6-4, 6-3 win Tuesday over Karolina Pliskova and into her 12th semifinal in New York, all the highly seeded women who were supposed to give her trouble are gone.

Stephens, the No. 3 seed, lost her quarterfinal match to No. 19 seed Anastasija Sevastova, 6-2, 6-3, in the brutal afternoon heat. The upset left Pliskova, whose No. 8 seed matches her ranking on the WTA Tour, as the last top 10 player in the draw.

Williams swatted her aside to notch her first win over a top 10 player since making her comeback.

“That’s a really big step for me. Shocking, my first top 10 win,” Williams said. “I really felt like I was playing well [last month] in Cincinnati, even though I lost. I was just on the verge. If I could have just had one more match before I played a top 10 player, I think I would have done better.

“I’m getting those matches now. Just was so light on the matches. So now I feel like I’m at a level where I can play and try to compete against these amazing women in the top 10.”

The highly anticipated rematch of a 2016 semifinal proved little problem for the 23-time Grand Slam champion, who fell behind 4-2 after a slow start but won the next eight games in a row.

Williams served 13 aces and hit 35 winners in a tight 84 minutes that could have left Pliskova with whiplash it turned around so quickly.

She closed with a final game that featured three aces and an overhead smash.

The six-time U.S. Open champ faces Sevastova, whom she has never faced, in the semifinals next. Should she beat the Latvian, Williams could face No. 14 seed Madison Keys, No. 20 seed Naomi Osaka, No. 30 seed Carla Suarez Navarro or the unseeded Lesia Tsurenko in the final Saturday.

No potential opponent can be dismissed, especially considering Keys made the final here last year, but Williams has reason to feel confident with her path ahead. She owns a combined 10-1 record against the four women, with the one loss coming against Osaka this year in Williams’s second tournament back after her time off.

Of all of the opponents she could have faced, Stephens would likely have challenged her the most. But just over 12 hours after the U.S. Open lost Roger Federer in the wee morning hours Tuesday, the defending champion fell at Arthur Ashe Stadium.

“I’m tight as f—, and it’s hot as f—!” Stephens yelled in one moment of frustration, just minutes after tournament organizers suspended play in the junior tournament because of extreme heat. All of those matches take place on the outer, roofless courts at Billie Jean King National Tennis Center where there is no shade, but temperatures soared on the tournament’s main stage as well. An extreme heat policy that grants an extra 10-minute break mid-match was in effect for all men’s and women’s singles matches Tuesday afternoon.

After the match, Stephens refused to blame the heat — or the sinus infection she said she has been playing with since Monday — and instead cited her failure to take advantage of early opportunities to get ahead on Sevastova’s serve.

“Yeah, it was just really hot. You can’t control the weather, can’t control what the tournament is going to do. You just have to go with it,” Stephens said. “Unfortunate that I played first match at 12 o’clock and it was so extremely hot, but it was hot for both of us. She handled it better. … Today was just a tough day. I didn’t play my best.”

Stephens looked a step behind from the start of the match and failed to convert seven break points in the first set against Sevastova, which put her in a dangerous position against a woman who entered the match having broken her opponent’s serve a tournament-leading 23 times.

Sevastova broke the 25-year-old American’s serve twice in the opening set, then broke her again to take a 2-0 lead in the second. She controlled the match from then on.

“When you don’t play the big points well and don’t take your opportunities early, that could affect the outcome of the match,” Stephens said. “I think today I didn’t play those points well at all, even at the end, in the second set.”

Sevastova retired in 2013, returned to the game in the same year and since then has played some of her best tennis in New York. She has made three straight quarterfinal appearances in New York, but Tuesday was her first breakthrough: The 28-year-old is the first Latvian woman to make the U.S. Open semifinals.

“I’m relieved that the match is over in this heat,” she said with a smile when asked how the win feels. “Yeah, how do you feel? You feel happy. I think you need some time to look back, to look at this journey. It was an amazing journey … right now I’m so in it, in the tournament, and you don’t feel it, you know. … So after I stop at some point I will look back at it and I will be proud of myself, for sure.”

First, Sevastova has her sights set on further complicating the draw.

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