Rafael Nadal's quest to defend his crown at Roland-Garros continued on Thursday after he overcame an early setback to defeat Diego Schwartzman 4-6, 6-3, 6-2, 6-2 and qualify for the 2018 French Open semi-finals.

He'll face another Argentinian foe in Juan Martin del Potro, who ousted Marin Cilic from the tournament with a 7-6 (5), 5-7, 6-3, 7-5 victory and qualified for just his second Grand Slam semi-final in the past five years.

Del Potro's win over Cilic means he'll compete in the Roland-Garros semis for the first time since 2009, and the victory also means he'll make his way back into the ATP's top four as of Monday, per tennis writer Jose Morgado.

Women's world No. 1 Simona Halep will retain that position after she made her way to the women's final for the second year in succession, beating third seed Garbine Muguruza 6-1, 6-4.

Her opponent will be American Sloane Stephens, who defeated compatriot Madison Keys 6-4, 6-4 to qualify for her second career Grand Slam final.

Read on for a roundup of Thursday's results from Roland-Garros, complete with a breakdown of the key stats, highlights and discussion of the updated draw in Paris.

Thursday's Results

Men's Singles

(1) Rafael Nadal bt. (11) Diego Schwartzman: 4-6, 6-3, 6-2, 6-2

(5) Juan Martin del Potro bt. (3) Marin Cilic: 7-6 (5), 5-7, 6-3, 7-5

Women's Singles

(1) Simona Halep bt. (3) Garbine Muguruza: 6-1, 6-4

(10) Sloane Stephens bt. (13) Madison Keys: 6-4, 6-4

Nadal swiftly turned his fortunes around against Schwartzman and booked his place in the French Open semis for an 11th time after rain delays meant he ended play on Wednesday 6-4 3-5 down to the South American.

The Spaniard's serve looked far more reliable when play resumed on Thursday, while Schwartzman struggled and suffered two breaks in each the third and fourth sets.

As Morgado noted in the aftermath of his latest win, Del Potro has a daunting task attempting to stop Nadal's flow in Paris:

José Morgado @josemorgado

Nadal into the #RG18 semifinals. Rafa in semis and finals at Roland Garros: 20-0.

Nadal won only 10 of 21 points played (47 per cent) on the first ball in his opening set with Schwartzman, compared with an average 72 per cent in the final two sets, per Roland-Garros' official website.

Schwartzman can take small consolation knowing he's the only player at the French Open so far this year to take a set from Nadal, who gave the impression in his post-match notes that fatigue may be setting in, per Reem Abulleil of Sport360.com:

Reem Abulleil @ReemAbulleil

Q. If I can make a parallel with Cristiano Ronaldo, Real Madrid doctors published medical results saying he has a body of a 23-year-old w 7% fat. Since you have the same age, how's your body..? Nadal: My body is about 40 years old, but I'm not really focusing on that.

Nadal fully acknowledged how the rain delay worked in his favour, too, as he seeks an 11th title on the clay of Roland-Garros, per BBC Sport: "I was able to stop, to think, to calm down and to see things a bit with more clarity."

Another Argentinian will hope to succeed where Schwartzman could not on Friday. Del Potro will face Nadal at Roland-Garros for the second time in their careers, with the first clash having taken place back in 2007.

Third-seed Cilic lost two points after the pair resumed play on Thursday poised at 5-5 in a first-set tiebreak, although he hit back to level in the second set despite hitting more double faults and unforced errors than his opponent.

Writer Tumaini Carayol touched on how Cilic came into the clash with a clear game plan, although Del Potro had the resources to manoeuvre his way to victory all the same:

Tumaini Carayol @tumcarayol

Del Potro is 2hr43 into a tennis match and he has hit 1 (one) forehand winner.

Del Potro was unable to hold back the tears upon completing his upset of Cilic, returning to a Grand Slam semi for the first time since last year's U.S. Open, and the Paris crowd celebrated the South American's achievement. 

As one world No. 1 progressed in the men's singles, so too did Halep in the women's, as she beat a worthy foe in Muguruza 6-1, 6-4.

Muguruza crucially converted only two of her eight break-point chances and was lacklustre with her second serve at times.

Journalist Rene Denfeld highlighted Halep's scary backhand skills:

René Denfeld @Renestance

Halep's average backhand speed today 121 km/h. Nadal's average backhand speed vs Schwartzman 120 km/h. As per Eurosport. K. #RG18

The Romanian has twice lost finals at Roland-Garros (2014, 2017) but can finally add a Grand Slam to her record if she beats Stephens, who also looked confident en route to a straight-sets win over close friend Keys.

Stephens maintained her perfect record against Keys and won for a third time in three meetings, and ESPN Stats & Info touched upon the new dynasty of American women's talent emerging:

ESPN Stats & Info @ESPNStatsInfo

Sloane Stephens & Madison Keys will face off in the first All-American women’s semifinal matchup at the French Open since 2002. The winner will be the 1st American woman without the last name Williams to reach the French Open final since Jennifer Capriati in 2001.

Tenth seed Stephens, 25, thus far appears to be the superior of the two talents and proved as much with her 6-4, 6-4 victory, breaking Keys early in both sets to steer her way to a relatively comfortable win.

Halep looks like the runaway favourite for Saturday's clash, although 2017 U.S. Open winner Stephens holds the advantage of having won a major and can clinch a second Grand Slam crown in nine months if she upsets the odds in Paris.