Keys ends Stephens hoodoo, Muguruza on track to retain title
Madison Keys defeated Sloane Stephens for the first time in her professional career on Friday to reach the semi-finals of the Charleston Open.
Keys had lost each of her previous three competitive meetings with fellow American Stephens, including the final of the 2017 US Open.
This time Keys broke her duck, winning 7-6 (8-6) 4-6 6-2 in the WTA Premier event on outdoor clay courts in South Carolina.
"It's always hard to play a friend, so on that side of it you're obviously not going to be saying 'come on' in each other's faces or anything like that," she said of the top seed.
"But, I mean, we've been friends forever. So if she circles a mark and says it's out, I'm going to believe her."
Keys will face Monica Puig for a place in the decider, the Puerto Rican having surprised Danielle Rose Collins in straight sets.
In the other quarter-finals, 2011 winner Caroline Wozniacki eased past Maria Sakkari to book a meeting with Petra Martic, who upset Belinda Bencic in straights.
In the Monterrey Open, top seed Angelique Kerber, a two-time beaten finalist, defeated Kirsten Flipkens 6-2 6-4, and she will now tackle Victoria Azarenka in the last four. The Belorussian ousted third seed Anastasia Pavlyuchenkova, a four-time winner of this WTA International event, 6-0 6-4.
Title-holder and second seed Garbine Muguruza needed a second-set tie-breaker to get the better of Kristina Mladenovic, setting up a meeting with Magdalena Rybarikova in the semi-finals.