Simona Halep went from out-of-sorts to on-target against Angelique Kerber, scrambling to every ball and staying the course to erase an early deficit.
Halep was my pick to win the French Open, and I truly hope she finally gets the money off her back. "So I think that's why I won today", Halep said.
Halep completed the 30th win over a German opponent and remained unbeaten in quarter-finals matches here at Roland Garros.
Serena Williams might have fancied meeting this version of Sharapova, who made six double faults and 27 unforced errors.
Romania's Simona Halep came from a set down to beat Angelique Kerber in 2 hours 14 minutes.
"I think my body will need a little bit of rest, but mentally I'm ready to go", said five-time major victor Sharapova.
Garbine Muguruza celebrates after victory over Maria Sharapova.
Nadal was broken three times and lost the opening set of his quarterfinal Wednesday against 11th-seeded Diego Schwartzman of Argentina by a score of 6-4.
In the other men's quarter-final, number three Marin Cilic and number five Juan Martin del Potro were at 5-all in a first-set tie breaker when the match-up of past US Open champions was stopped. She hurried up her strokes and easily Halep sealed the eight win in as many matches against a lefty opponent and against a top 20 player this season.
Service breaks were exchanged at the start of the second set but Muguruza is a far steelier player than four years ago and Sharapova did not get a sniff in the next five games as the Spaniard reached her fourth Grand Slam semi-final.
The 2012 and 2014 Paris champion, who missed the 2016 tournament because of a doping ban and previous year when she was refused a wild card, was broken six times, committed 27 unforced errors and won just five points on her own serve in the second set.
On Wednesday, Halep looked anything but the top seed, slipping 4-0 down in the first set before she rallied to defeat Kerber, a two-time major victor who had exited in the first round in Paris in the last two years. "If I do that, I will be okay after the match, no matter the result". That she's into her first Slam semifinal on Roland Garros' red clay may seem a surprise to many, but Keys has had European clay success before.
"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".