The 10th seed, who beat Keys to win the US Open last year, showed impressive patience in some cat-and-mouse exchanges and eventually overpowered the 21-year-old with her bigger game on Tuesday.
"I love playing here".
"I'm very happy to win in straight sets". And then I think we fell into a nice rhythm here again and things are okay.
She won on her first match point with a backhand victor down the line.
Stephens reached her first Grand Slam semifinal in 2013; Keys did it two years later.
This match was a rematch of the final at Flushing Meadows from September a year ago where Keys won just three games in a match where Stephens secured the title after just one hour of play and did prove to be more competitive.
"When we get on the court, it's time to compete but before that, we are not going to be weird and awkward and make it weird for each other", Stephens said after her quarterfinal defeat of Daria Kasatkina.
"When we get on the court, it's time to compete", Stephens said.
Muguruza's last stand came at 4-all in the second set, a 13-minute game in which she held three break points. An elapsed time of nine months that Keys said feels "more like 12 years" - the natural observation of a player in the midst of a visible growth spurt.
Friends Madison Keys and Sloane Stephens will face off in the French Open women's semifinals on Thursday, June 7. "I obviously rely on what I learned there and how to manage my emotions and manage the moment". But in tennis, you never know, so I will stay chill. It's just how it's happened for me", Stephens said, "I think once I get going in a tournament, I'm pretty consistent, which is good.
Cecchinato struggled to comprehend his triumph, coming just two years after his career was nearly derailed when he became embroiled in match-fixing allegations. "I will try my best", Haleptold the crowd at Court Phillipe Chatrier, "and hopefully I will be better than past year". She is playing with aplomb rather than angst on a surface she used to consider foreign soil in every way, regarding it instead as fertile ground. "So to be here from there, I think is rewarding, because those times were not easy". Thursday's match will mark their first apperances in the semifinals at Roland Garros.
The imposing Argentine then walked over to the side of the court and began eye-balling a row of spectators. "It's so good for me, for my team, for my family".