It was another case of so near and yet so far this year for the evergreen Williams, who was beaten in the final of both the Australian Open and Wimbledon nine years after her last grand slam title. Interestingly, there will be a final round for both the players Stephens and the Keys on Sep 10th.
Keys, who was absent from the first two months recovering from wrist surgery, delivered an old fashion thrashing as she needed just 66 minutes to beat Vandeweghe, who also lost in the Australian Open semi-finals.
Williams has the opportunity to enter into her third major final of the season.
"I've known her for a long time".
Keys wins her first grand slam title. She broke Keys' serve twice to run away with it 6-3.
Stephens, who has a career-high ranking of 11 in 2013, dropped to 957 just two months ago but since then she has won 14 of 16 matches. I knew I was going to have to play my way into shape and I've done that pretty well.
ESPN Tennis Triumph: US Open Women's Championship Ratings 36 Percent Higher
And speaking at the trophy presentation, Stephens said: "I should just retire now, I told Maddie I'm never going to be able to top this.
I said to her that I wished it could have been a draw".
Williams's level lifted as she stormed through the second set, her power helping her level the match.
She will move to 22nd if she loses, and possibly as high as 15th if she defeats compatriot Madison Keys to win the title.
"Madi is one of my best friends on tour and to play her here, I wouldn't have wanted to play anyone else". She the roared back in the second and didn't even allow Stephens to hold serve a single time.
Williams said, "It was definitely a contrast of play".
"I really feel that this success of the Americans right now is largely due to Serena and Venus Williams and the impact that they have had on the sport and on young girls", Evert said.
McGregor live gate falls well short of record
Kavanagh - who is now in Florida - added: "The Nate Diaz trilogy fight at lightweight is what I'd personally like to see next". As impressive as the gate was, it wasn't enough to break the record set by Mayweather's bout against Manny Pacquiao.