Alexander Zverev ousts Rafael Nadal ahead of semifinals at Madrid Open

Alexander Zverev ended his winless streak on clay against Rafael Nadal on Friday, keeping the Spaniard from winning a sixth Madrid Open.

Zverev defeated Nadal 6-4, 6-4 in the quarterfinals, picking up his third consecutive win over the 20-time grand slam champion — but first on clay. His previous two wins over Nadal were on indoor hard courts.

"Beating Rafa on a clay court is the hardest thing in our sport," Zverev said. "Not many people have done it. This week so far it's been incredible for me. It's an incredible feeling right now."

The sixth-ranked German broke second-ranked Nadal's serve twice in the first set, rallying from 4-2 down, and once in the second. He conceded only two break opportunities.

"Playing against one of the best players in the world, under these circumstances, with this speed of the court, is very difficult to still (feel) confident," Nadal said. "I tried, but the serve was difficult to control today. Well done for him."

Nadal, who is preparing to play for a 14th title at the French Open, had been improving after a slow start to his clay season. He lost to Andrey Rublev in the Monte Carlo quarterfinals then beat Stefanos Tsitsipas in the Barcelona Open final.

Dominic Thiem defeats John Isner

Zverev will next face Dominic Thiem in a rematch of the 2018 final. Thiem, who lost to Zverev in straight sets in the Spanish capital three years ago, defeated John Isner 3-6, 6-3, 6-4.

The fourth-ranked Austrian capitalized on two of his four chances to break Isner's serve, and that was all he really needed.

Thiem broke the tall American on his first chance in the second set and once more in the third to reach the semifinals in Madrid for the fourth straight time.

"He is one of the best servers in history, especially here in the altitude. His serve is bouncing so high and it's so difficult to return," Thiem said. "I really stayed focused, with a good fighting spirit. Against guys like him, a few points decide and that's when I saved the break points in the beginning of the second set."

Thiem saved four break points in the fifth game of the second set, then broke Isner's serve in the next game to take the match to a third set. The Austrian squandered another break chance in the first game of the deciding set but capitalized again at 4-4.

U.S. Open champion Thiem has surprised himself in his first tournament since mid-March.

"I am surprised to be in the semifinals. I didn't expect that. I was just expecting to hopefully play one or two good matches here against top opponents," Thiem said. "That's amazingly good to get at least four matches on a top level."

Isner served more than 100 aces in his four matches in the Spanish capital, where the high altitude adds speed to the balls and makes the clay courts faster.

The American had 18 aces on Friday, and said his serve was the only reason he stayed in the match.

Later Friday, eighth-seeded Matteo Berrettini faced Cristian Garin, and Alexander Bublik took on Casper Ruud in the other quarterfinals.