The 10th-seeded Stephens had little trouble beating No. 14 Daria Kasatkina 6-3, 6-1 Tuesday on Court Philippe Chatrier.

She clinched the victory on her first match point with a forehand winner from the baseline.

"I thought I played pretty solid," Stephens said. "I knew that every time you go into a match there are a little bit of nerves that go into it. I knew I had to come out and keep swinging. Sometimes I start well and sometimes a little sluggish. I knew I needed to keep swinging no matter what, even if it was very close, so that's what I did. And when I got my opportunity at 4-3 to break, I was like, it's go time."

Stephens next faces Keys in a rematch from the US Open final.

Keys also reached her first French Open semifinal by defeating unseeded Yulia Putintseva 7-6 (5), 6-4. The 13th-seeded Keys has not lost a set at Roland Garros.

"When we get on the court, it's time to compete," Stephens said of facing her friend. "But before that, we are not going to be weird and awkward and make it, like, weird for each other. Now I just have to go find her, because I need to tell her some juicy stuff. I just went and searched for her in the training room.

"Yeah, I think everything will be normal. And then when we get on the court, it's time to compete. It's go time. Until then, we're the same girls as always."

While Putintseva regularly lost her composure, Keys stayed calm throughout. The big-hitting American secured victory on her first match point with a powerful serve that clipped Putintseva's racket and flew into the crowd.

Keys' box, including three-time major winner Lindsay Davenport, rose to acclaim the American.

The 98th-ranked Putintseva was trying to become the first player from Kazakhstan to advance to a Grand Slam semifinal.

She had her chances against Keys, troubling her with deft drop shots and spinning, looping forehands, but could not hold her nerve.

After losing the first-set tiebreaker, Putintseva started ranting at her box and struck the ground with her racket in frustration.

Known for her short fuse, she lived up to it, regularly spinning around to glare at her box with looks of incomprehension and hand-flapping gestures, or at other times mumbling to herself in frustration.

In the second game of the second set, she was convinced an incorrect call went in favor of Keys and asked the chair umpire to come down and check it.

"My God," Putintseva said as she walked away. "I can't believe ... unbelievable."