Sloane Stephens was two points away from losing her semifinal at Arthur Ashe Stadium on Thursday night, but the young American came back to defeat seven-time major champion Venus Williams 6-1, 0-6, 7-5 and reach her first US Open final.

US Open 2017 women’s final preview

Stephens, 24, will face 22-year-old Madison Keys in the women’s title game, which will begin at 4 pm EST on Saturday. No. 15 seed Keys advanced easily by cruising past 20th-seeded American CoCo Vandeweghe 6-1, 6-2 in just over one hour in Thursday’s first semifinal.

“I have a lot of grit,” said Stephens, who is ranked 83rd after undergoing surgery on her left foot in January and is the fourth unseeded finalist at the tournament in the Open era, which dates to 1968. “I don’t give up. Like, I’m not just going to give it to someone. I’m not just going to let them take it from me.”

Ninth-seeded Williams, 37, was hoping to become the oldest woman to win a Grand Slam in the Open era. She was also striving to reach her third major final of 2017 (after reaching the title game at the Australian Open in January and Wimbledon this summer). Williams made her US Open debut in 1997 and reached the final that year. The American has won the tournament at Flushing Meadows, Queens twice, in 2000 and 2001.

“I just wasn’t playing well. Those are moments where you have to dig deep and figure out how to get the ball on the court and have a big game. I can’t be tentative and try to figure out how to put that ball in,” Williams said. “Clearly she’s seen me play many, many times. I haven’t seen her play as much,” she added of Stephens.

Williams finished with six double-faults and a total of 51 unforced errors, 24 more than Stephens.

Williams was up 5-4 with Stephens serving at 30-all in the final set, and was thus just two points away from clinching the match. A 25-stroke point ensued, until Stephens fired a backhand passing winner down the line, then turned around and pumped her fists in excitement.

At 5-5, Stephens broke with a fantastic arching winner — “That lob-thingy,” as she referred to it after the match — that led to a standing ovation from the crowd at Billie Jean King National Tennis Center. Stephens then managed to return a short ball by making a full sprint to the net and hit the shot from an impossible angle.

“There was nothing I could do about those shots,” Williams said.

Keys — who missed the first two months of the year after undergoing left wrist surgery and needed another procedure in June due to pain in that arm — recorded 25 winners and only nine unforced errors in her victory over 25-year-old Vandeweghe.

“It was kind of one of those days where I came out and I was kind of in a zone,” Keys said of her play Thursday, “and I just kind of forced myself to stay there.”

Keys never faced a break point during her semifinal. Play was delayed for more than five minutes when Keys left the court to have her upper right leg taped at 4-1 in the second set.

“Madison played an unbelievable match,” said Vandeweghe, who couldn’t help but cry during her news conference. “I didn’t really have much to do with anything out there.”

Stephens and Keys have only played once before, on a hard court at Miami in 2015. Stephens won in straight sets.

The two youngsters are reportedly close off the court.

“She’s one of my closest friends on tour. It’s obviously going to be tough,” Stephens said. “It’s not easy playing a friend.”

Keys and Stephens — the first All-American women’s final at the US Open since 2002 — will face off at 4 pm EST on Saturday at Arthur Ashe. The match will air on ESPN and online at WatchESPN.

On the men’s side, 28th-seeded South African Kevin Anderson and 12th-seeded Spaniard Pablo Carreño Busta will face off in the first semifinal at 4 pm EST on Friday. The second men’s semifinal will begin at 5:30 pm EST and will see top seed Rafael Nadal play Juan Martin del Potro, the 24th-seeded Argentine who eliminated Roger Federer in the previous round to erase fan’s hopes for the first-ever Nadal-Federer final at Flushing Meadows.

The men’s final will begin at 4 pm EST on Sunday. All three remaining men’s games will also air on ESPN and online at WatchESPN.

NEW YORK, NY – SEPTEMBER 07: Sloane Stephens of the United States returns a shot against Venus Williams of the United States during their Women’s Singles Semifinal match on Day Eleven during the 2017 US Open at the USTA Billie Jean King National Tennis Center on September 7, 2017 in the Queens borough of New York City. (Photo by Abbie Parr/Getty Images for USTA)

Juan Martin del Potro ended Roger Federer’s hopes of securing a record-stretching 20th Grand Slam title and a sixth U.S. Open trophy by defeating the third-seeded Swiss 7-5, 3-6, 7-6 (10-8), 6-4 in a thrilling quarterfinal at Arthur Ashe Stadium on Wednesday night, Day 10 of the the tournament.

US Open 2017 Semifinals News

The 24th-seeded Argentine — who will be 29 later this month — beat Federer in the 2009 Final in Flushing Meadows, Queens and will next face World No. 1 Rafael Nadal in Friday’s second semifinal.

Tennis fans had been eagerly hoping for the first-ever US Open matchup between Federer and the top-ranked Spaniard, who advanced by eliminating Russian teenager Andrey Rublev 6-1, 6-2, 6-2 on Wednesay, but del Potro dashed those hopes.

The first men’s semifinal on Friday will see 28th-seeded South African Kevin Anderson play 12th-seeded Spaniard Pablo Carreño Busta. 

Del Potro hit big serves and huge forehands and remained concentrated when Federer appeared to regain control in the second set. In the first set, the Argentine boasted a 79 first-serve percentage.

“I think I played my best match of the tournament, I did everything well,” said del Potro. “I served so good, I hit my forehand as hard as I could and I think we played a great match and I think I deserved to win.”

Del Potro had a chance at 5-5 in the first set when Federer recorded a double fault and then smacked a strong forehand shot, with which he also took the opening set over the Swiss in the following game.

Federer — who had been suffering from back problems — barely sat during the pause between sets, and he broke for 3-1 with a forehand passing shot as del Potro’s serve began to falter, and the Swiss easily won the second set.

After del Potro regained control in the third set tie-breaker — during which Federer double-faulted in the second game — the Swiss saved another break point in the fourth game of that set, setting up one for himself in the seventh. Del Potro lost that seventh game with a double fault.

In the tie-breaker, Federer took a 6-4 lead to earn two set points, although del Potro saved them with an amazing service return on the baseline and a powerful serve.

A Del Potro double fault gave Federer another opportunity, but the Swiss messed up a backhand half-volley and the Argentine took the set with a forehand winner on the fourth set point.

After forcing Federer to hit a volley long in the final set, del Potro broke for 3-2 with an amazing cross-court backhand winner.

The sold-out crowd of 23,771 at Arthur Ashe roared when the Argentine won the match with a powerful forehand winner.

“I think it’s my home court, too, you make me feel happy every time I play here and I love your support guys. I love to see you cheer for me,” del Potro told the crowd. “After all my injuries and surgeries … New York is my favorite tournament, my favorite city to play tennis.”

 On the women’s side, all four ladies playing in this year’s semifinals are American. This marks the first time since 1985 that four U.S. women advance to the semifinals of a Grand Slam tournament, and the first time four American female players reach the US Open semis since 1981.

Venus Williams, Sloane Stephens, Madison Keys and CoCo Vandeweghe have all made it through to the last four. Both women’s semifinals will be held on Thursday night and will air on ESPN.

Williams will face Stephens in the first semifinal at 7 pm EST, after the latter advanced by beating 16th-seeded Latvian Anastasija Sevastova in three sets on Tuesday.

In her last three tournaments — Toronto, Cincinnati and US Open — Stephens reached the semi-finals. Before Toronto, Stephens ranking had dropped to 934 in the world after a year of inaction. By making the last-four at Flushing Meadows, Stephens has assured that she will be back in the top-35.

The 24-year-old Stephens — who is playing in her first US Open — is also seeking her first Grand Slam title after undergoing foot surgery in January and serving as a broadcaster earlier this year as well.

No. 15 seed Keys and No. 20 seed Vandeweghe will face off in the second semi-final at 8:15 pm EST on Thursday. Keys, 22, advanced by defeating Estonian Kaia Kanepi 6-3, 6-3 on Wednesday, while 25-year-old Vandeweghe eliminated top-seeded Czech Karolína Plíšková with a 7-6 (7-4), 6-3 victory on Wednesday.

Keys underwent her second wrist surgery in 10 months after a devastating three-set loss at the French Open in May. Thursday’s game will be her second Grand Slam semifinal: she previously reached the last four at the Australian Open in 2015. Vandeweghe, meanwhile, has defeated two World No. 1 players thus far in 2017: Pliskova and German star Angelique Kerber, whom she beat in Melbourne in January.

NEW YORK, NY – SEPTEMBER 06: Juan Martin del Potro of Argentina returns a shot against Roger Federer of Switzerland during their Men’s Singles Quarterfinal match on Day Ten of the 2017 US Open at the USTA Billie Jean King National Tennis Center on September 6, 2017 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Clive Brunskill/Getty Images)