Somehow, this plucky, reliable Grand Slam final mainstay, Halep, is about to oppose a player who lately had nine mostly clunky Grand Slams and then an 11-month hiatus, yet the latter will be the one with the major title already.
Halep's third final at Roland Garros comes 40 years after the first and only Romanian triumph in a women's final at the French Open.
Muguruza had lost all three previous times she faced Sharapova, whose five grand slam titles include two at Roland Garros.
But it took Muguruza quite a while to get going against Halep, who managed to keep sending ball after ball back over the net.
After Halep's 6-1, 6-4 win, Muguruza said: "Her shots were very, very deep and very aggressive, constantly".
Backed by fans who loudly chanted her first name between games, Halep went ahead 3-0 in only 15 minutes with the help of only one victor.
It was 5-0 by the time Muguruza eventually claimed a game.More news: Bill Clinton: I Do Not Owe Monica Lewinsky an Apology
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In short, this is proper, pressure second-week of a grand slam tennis.
She also was coming off a lopsided victory in the quarterfinals a day earlier, overwhelming Sharapova 6-2, 6-1. Her wins over Muguruza and Angelique Kerber have taken more than 3.5 hours combined. "I think Serena hated me for being the skinny kid who beat her, against all odds, at Wimbledon", Sharapova wrote. Now she gets her fourth chance to do exactly that. I was, like, 'OK, next round.' That's just kind of how you handle it.
I can only conclude that the market has grossly over-reacted to seeing Muguruza's beating of Sharapova yesterday afternoon, and made her a false favourite for this clash - Halep at [2.10] is today's recommendation. "I think there are a lot of good things like the way my body has handled the long matches that I have played, the back-to-backs".
"I didn't play flat any more, more top-spin, and I made her run a little bit more", she said. Some of this is X's and O's; Sloane makes you hit the extra ball and has played terrific tennis in the matches, and Keys has missed too much. She knows she needs to win one of these Slams, and she's confronted this missing element head-on.
Halep is aware she can not afford another poor start on Thursday against 24-year-old Muguruza who has been tested just once in Paris and that was in the first round where fellow former victor Svetlana Kuznetsova pushed her to a tiebreak in the first set.
Regardless of the result, the 25-year-old Stephens will become the first American to break into the top five in the WTA rankings since Lindsay Davenport - Keys's coach - in 2006.
"I know that she's strong opponent".
Keys said before their semifinal meeting at Roland Garros that her 6-3, 6-0 loss in September's decider at Flushing Meadows felt like it was "12 years ago".