Rafael Nadal was locked in a French Open quarterfinal tussle with Argentinian Diego Schwartzman when rain ended play on Wednesday, after Garbine Muguruza thrashed Maria Sharapova to reach a last-four showdown with top seed Simona Halep.

World number one Nadal lost his first set at Roland Garros in three years, and when bad weather first interrupted the match the 10-time champion was in serious trouble with Schwartzman up a break in the second.

The players briefly returned to the court, giving the 32-year-old Spaniard enough time to reel off three straight games, but the rains came again for a second and final time when he was serving for the set.

The match will resume on Thursday with Schwartzman leading 6-4, 3-5 (15-30).

The winner of the match will play either third seed Marin Cilic or Schwartzman's compatriot Juan Martin del Potro.

Their last-eight match was level at 6-6 (5/5) in a first-set tie-break on Court Suzanne Lenglen after Del Potro had earlier missed five break points.

Nadal had won 37 consecutive sets at Roland Garros since his 2015 quarterfinal defeat by Novak Djokovic, but dropped serve three times to the enterprising Schwartzman in an exciting opener.

The 25-year-old took his third set point with a rasping forehand up the line, after being made to wait when a spectator fell ill in the stands.

Nadal made 14 unforced errors and struck just four winners in a poor first set, before having both of his wrists strapped by the trainer.

Schwartzman, who had never even reached a Grand Slam quarterfinal until last year's US Open, broke first in the second set as Nadal uncharacteristically blew a 40-15 lead, capped by two wild forehands.

The Court Philippe Chatrier, which was half-full during Muguruza's dismantling of Sharapova earlier in the afternoon, was packed with a crowd living every point when rain started to fall.

Play continued though, with the set following a similar pattern to the first, as Nadal broke back before dropping his serve to 15.

The players were forced off the court for 40 minutes, but when they returned Nadal levelled for 3-3 and let out a trademark roar of 'vamos'.

Muguruza condemned Sharapova to her heaviest Grand Slam defeat in more than six years and will face top seed Simona Halep for a place in the final against either Sloane Stephens or Madison Keys.

The Spanish third seed, who was the champion in Paris in 2016, swept aside the Russian 6-2, 6-1 in just an hour and 10 minutes.

Her semifinal with Halep will also decide the world number one spot next week.

Current number one Halep made the semifinals for the third time by battling past Germany's Angelique Kerber 6-7 (2/7), 6-3, 6-2.

"I am very pleased to be in another final in Paris," said Muguruza who has yet to drop a set in the tournament and claimed her first win over Sharapova in four meetings.

Sharapova made 27 unforced errors, was broken six times and served six double faults in only her fifth loss from 25 Grand Slam quarterfinals.

"To have had the victories that I have had, to have the results that I have, obviously moving a step in the right direction," said the five-time Grand Slam champion who had made the last-eight in Madrid and semis in Rome in the run-up to Paris.

"But today was certainly not one of those steps."