Their success attests to the new depth of American women's tennis and confirms the exceptional nature of two young women who might have seemed to be moving at a slow pace in turning their potential into success but have gotten there all the same.
Stephens, who ranked 957th in the world in late July when she returned from an 11-month injury absence and was unseeded here as the 83rd-ranked player, played a gutsy third set against seven-time Grand Slam winner
Keys, who acknowledged she didn't expect to win here and was "just going match by match," savored the night that much more because she and Stephens have become friends over the years. "I can't think of a better person to have this first experience with," Keys said.
Stephens, 24, has always been a good defender but was forced to refine other elements of her game. She had to become more nimble with her footwork — which is now one of her strengths — add nuances that give depth and extra dimensions to her power-dependent game, and become more positive when things aren't going so well, as in Williams' second-set revival Thursday. In the third set, though, Stephens discovered she had another asset to tap after Williams took a 5-4 lead and was two points away from victory at 30-all.
"That I'm a real fighter, that I have a lot of grit. Surprising," said Stephens, who hit a spectacular backhand passing shot to get back into that 10th game and trigger a match-closing roll.
"I don't give up. I'm not just going to give it to someone. I'm not just going to let them take it from me. I'm going to make sure I give everything that I have, and I leave everything on the court at all times, no matter what."
It was a difficult loss for Williams, whom Keys and Stephens have said they idolize. Williams, told of their respect for her, was unmoved, probably because her loss was so fresh. "To be honest, I'm definitely here to win my matches, not for consolations," said Williams, who was serenaded by a standing ovation from Stephens and the appreciative fans as she exited the court.
For the last few years Stephens has been, in some ways, a victim of her own success. She was 19 when she defeated
"I was a baby then," Stephens said of that 2013 semifinal. "I didn't know as much as I know now. I think a lot of life has happened. I have been through a lot."
Keys has had her share of tribulations, too, most recently two wrist surgeries that also made her a spectator during this year's Australian Open. Seeded No. 15 here, Keys was sharp from the start against No. 20 seed Vandeweghe and never faced a break point. Keys hit 25 winners and made only nine unforced errors.
"I thought at some point she might start running a little bit colder than what she was doing," said Vandeweghe, who teared up several times during her post-match news conference. "I was fighting as hard as I could for as long as I could but she stayed hot the whole time."
Keys took a medical timeout after she tweaked something in her thigh just to be sure it would not become a bother, but that was the only blip on her otherwise joyous night. "It feels absolutely amazing," she said. "These are the moments growing up that you dream about."
For Keys or for Stephens, a dream will come true on Saturday.