Paris - Novak Djokovic on Monday became the first man to reach the French Open quarter-finals for 10 successive seasons while defending women's champion Simona Halep swept into the last eight in just 45 minutes.
Top seed and world number one Djokovic continued his bid to hold all four Grand Slam titles simultaneously for the second time by thrashing Germany's Jan-Lennard Struff 6-3, 6-2, 6-2.
The 32-year-old will now face fifth seed Alexander Zverev in what will be his 13th appearance overall in the quarter-finals in Paris.
"It was tricky with the rain, but that's Paris," said the 2016 champion after playing in drizzly conditions.
"I'm really confident with my serve. I hope it continues like that."
Only Australian great Rod Laver has held all four majors at the same time twice before, after his calendar Grand Slams in 1962 and 1969.
German fifth seed Zverev reached his second successive Roland Garros quarter-final with a 3-6, 6-2, 6-2, 7-6 (7/5) win over Italy's Fabio Fognini.
Last year he achieved his best run at the Slams, making the quarter-finals where he was defeated by eventual runner-up Dominic Thiem.
"It's going to a great match and a tough battle against Novak, the world number one, it's going to be interesting," said Zverev who is 2-2 against Djokovic in his career.
However, he won their only meeting on clay in the Italian Open final in 2017 in straight sets and beat him in the ATP Finals later that year.
Japanese seventh seed Nishikori came back from 1-4 and 3-5 down in the final set to beat Benoit Paire of France and set-up a quarter-final clash on Tuesday against defending champion Rafael Nadal.
Nishikori won 6-2, 6-7 (8/10), 6-2, 6-7 (8/10), 7-5 in a shade under four hours to reach his third last-eight match at the French Open.
"He almost had it today," said Nishikori who had led two sets to one when the last-16 tie was suspended on Sunday.
"He served for the match at 5-3 but I just tried to fight and play one point at a time."
The 29-year-old Japanese could have wrapped it up in the fourth set when he had two match points but squandered both, the second on a double fault.
Paire, the world number 38 who was trying to make the quarter-final of a Slam for the first time, was eventually undone by 15 double faults and 79 unforced errors.
Nishikori has only defeated 11-time French Open champion Nadal twice in 12 meetings with both of those wins coming on hard court.
The Spaniard, celebrating his 33rd birthday on Monday, has won all four of their meetings on clay.
"It's going to be a tough match, he's the greatest ever clay court player," said Nishikori.
For Paire, it was an opportunity lost.
"I should have lost it in three or four sets but I should have won it in the fifth set," said the 30-year-old.
French interest in the singles ended for another year just a few hours later when 14th seed Gael Monfils was defeated 6-4, 6-4, 6-2 by Austrian fourth seed Thiem, the 2018 runner-up.
The Austrian pulled off a memorable 'tweener' shot between his legs in the match.
"When it goes in, it's called a hot-shot," said the 25-year-old.
Thiem will be playing in his fourth successive quarter-final where he will face 10th-seeded Russian Karen Khachanov who defeated two-time semi-finalist and eighth seed Juan Martin del Potro 7-5, 6-3, 3-6, 6-3.
The 23-year-old Khachanov is the first Russian man to make the last eight in Paris since Mikhail Youzhny in 2010.
Halep reached her fourth French Open quarter-final with a 45-minute thrashing of Polish teenager Iga Swiatek.
The Romanian third seed raced to a 6-1, 6-0 win as Swiatek failed to hold serve in the match.
Halep will face American 17-year-old Amanda Anisimova, who defeated Spain's Aliona Bolsova 6-3, 6-0, for a semi-final place.
"Kind of perfect," said Halep after her win.
World number 51 Anisimova, meanwhile, became the first player born in the 2000s -- man or woman -- to make a Grand Slam quarter-final.
The players who stunned top seed Naomi Osaka and 23-time major winner Serena Williams got a taste of their own medicine.
American 14th seed Madison Keys reached the quarter-finals for the second successive year with a 6-2, 6-4 win over Katerina Siniakova, the conqueror of US and Australian Open winner Osaka.
Keys, who went on to reach the semi-finals in 2018, next faces Australian eighth seed Ashleigh Barty.
"I was really happy to close it out as playing three sets in these heavy conditions does not sound like much fun," said the 24-year-old Keys.
Barty beat Sofia Kenin, who stunned Williams in the third round, 6-3, 3-6, 6-0.
Results from the ninth day of the French Open on Monday (x denotes seeding):
Novak Djokovic (SRB x1) bt Jan-Lennard Struff (GER) 6-3, 6-2, 6-2
Alexander Zverev (GER x5) bt Fabio Fognini (ITA x9) 3-6, 6-2, 6-2, 7-6 (7/5)
Dominic Thiem (AUT x4) bt Gael Monfils (FRA x14) 6-4, 6-4, 6-2
Karen Khachanov (RUS x10) bt Juan Martín Del Potro (ARG x8) 7-5, 6-3, 3-6, 6-3
Kei Nishikori (JPN x7) bt Benoît Paire (FRA) 6-2, 6-7 (8/10), 6-2, 6-7 (8/10), 7-5
Madison Keys (USA x14) bt Katerina Siniakova (CZE) 6-2, 6-4
Ashleigh Barty (AUS x8) bt Sofia Kenin (USA) 6-3, 3-6, 6-0
Simona Halep (ROM x3) bt Iga Swiatek (POL) 6-1, 6-0
Amanda Anisimova (USA) bt Aliona Bolsova (ESP) 6-3, 6-0