JOIN USRafael Nadal broke John McEnroe's 34-year record on Thursday by winning his 50th consecutive set on clay at the Madrid Open.
The world number one cruised to a 6-3, 6-4 victory over Diego Schwartzman, and the straight-set victory means he establishes a new Open era best for consecutive sets won on a single surface, passing McEnroe's 49 on carpet in 1984.
McEnroe also won the Madrid Open Indoor title that year and Nadal may be about to follow suit in the Spanish capital, with Austrian Dominic Thiem up next in the quarterfinals on Friday.
Nadal had insisted before the match this latest milestone had barely crossed his mind but if nothing else, it is testament to the 31-year-old's relentless consistency over the past 12 months.
The run includes tournament triumphs in Barcelona, Monte Carlo and last year's French Open, where he will be the clear favourite later this month to claim a 17th major crown.
Schwartzman, ranked 16th in the world, briefly threatened a comeback on Manolo Santana court when he broke back at 4-3 in the second set.
But the Argentinian double-faulted to give his opponent a second break in the very next game, as Nadal sealed a straight-forward victory in an hour and 44 minutes.
Juan Martin Del Potro, however, will not join him in the last eight, the Argentinian leading 4-0 in a third-set tie-break but still losing 3-6, 6-4, 7-6 (8/6) to Serbian qualifier Dusan Lajovic.
Lajovic will now face South Africa's Kevin Anderson, who overcame Philipp Kohlschreiber.
"I think I can improve a lot of things towards Rome and Roland Garros," Del Potro said. "I can level up my game. Right now I'm quite calm."
Maria Sharapova also lost in three sets to Kiki Bertens of the Netherlands while Halep, the champion in 2016 and 2017, was blown away by Karolina Pliskova.
It means Pliskova, the sixth seed, is the highest-ranked player left in the women's draw after Caroline Wozniacki, Garbine Muguruza, Elina Svitolina and Jelena Ostapenko all lost earlier in the week.
Pliskova's 6-4, 6-3 win sets up a showdown with either two-time Wimbledon champion Petra Kvitova or the talented Russian Daria Kasatkina for a place in the final on Saturday.
Sharapova is set to climb inside the top 40 next week and the 31-year-old will be encouraged by her week's work, where she showed signs she is finding her rhythm.
The Russian arrived on the back of four consecutive defeats but three victories and a narrow 4-6, 6-2, 6-3 loss to Bertens suggests she could be a threat at the French Open later this month.
"It was great to get those wins against those players," said Sharapova, the 2014 champion in Madrid.
"But there's a reason I came up short today. You also want to evaluate that and go back to the drawing board and start over again."
Bertens, meanwhile, will now face France's Caroline Garcia, who eased past Carla Suarez Navarro 6-2, 6-3.
Novak Djokovic's conqueror, Kyle Edmund, maintained his strong run with a comfortable 6-3, 6-3 win over eighth seed David Goffin.
Edmund will face Denis Shapovalov, who came through his all-Canadian clash with Milos Raonic, 6-4, 6-4.
Second seed Alexander Zverev beat Argentina's Leonardo Mayer and will now take on John Isner, who beat Pablo Cuevas.