Alexander Zverev beat Karen Khachanov while Dominic Thiem got past Kei Nishikori to set up a marquee quarterfinal matchup.
PARIS (AP) Second-seeded Alexander Zverev has reached his first Grand Slam quarterfinal the hard way, beating Karen Khachanov 4-6, 7-6 (4), 2,6, 6-3, 6-3 on Sunday for his third straight comeback win in five sets.
The latest gritty victory came with the usual temper flare-ups from Zverev. But the German player also showed, once again, that he knows how to dig deep when it matters. In all three of his five-setters at Roland Garros he has trailed 2-1 in sets.
''I'm young. I might as well stay on court and entertain you guys,'' the 21-year-old Zverev joked with the crowd. ''This definitely paid off, the hours in the gym every day ... Everything comes together slowly and I'm happy to be here.''
Zverev says he spends up to four hours each day working on weights and fitness in the gym.
He might well need to up that schedule considering his quarterfinal opponent is No. 7 Dominic Thiem of Austria, who is one of the fittest players on the men's circuit and has reached the past two semifinals at Roland Garros.
Thiem beat No. 19 Kei Nishikori of Japan 6-2, 6-0, 5-7, 6-4 on Court Philippe Chatrier. He missed an easy forehand on his first match point, biting down on his fingers in frustration. He converted on his next chance when Nishikori's looping return landed long.
Nishikori won just 14 points in the first set and nine in the second, losing to Thiem for the first time.
''The first two sets were amazing,'' Thiem said.
On Court Suzanne Lenglen, Zverev's smash at the net gave him match point, which he took when Khachanov netted a forehand.
Zverev sank to his knees in celebration. He then patted Khachanov, a friend from their junior days, sympathetically on the chest before pumping his arms in celebration.
As in the previous two rounds, Zverev was struggling for consistency. This was illustrated in the 10th game of the second set.
Zverev serving for the set at 5-4, he soon trailed 0-40.
Then, in a blur Zverev won the next four points to give himself a set point - only to miss a smash from near the back of the court. An ace gave him another set point but he missed that one, too, putting a low volley into the net.
On his third set point, the erratic Zverev found the net again with a sloppy backhand. Khachanov punished him and broke for 5-5.
The second-set tiebreaker was scrappy, Zverev clinching it with an ace out of Khachanov's reach to level the match.
Zverev has youth on his side, but he has been spending long on court and his body is showing it.
At the start of the fifth set, he had a medical time out for treatment for an apparent blister on his left foot.
It did not seem to impede him, however.
He broke immediately for a 1-0 lead and jumped around on court, waving his arms to get the crowd going.
Later Sunday, Novak Djokovic was facing Fernando Verdasco on Court Philippe Chatrier, where he won the last of his 12 major titles in 2016.
In women's play, 13th-seeded Madison Keys reached the quarterfinals for the first time at Roland Garros after beating No. 31 Mihaela Buzarnescu of Romania 6-1, 6-4 on Chatrier.
''I had an extremely tough opponent and she raised her level at the end, so I'm very happy to get that win,'' Keys said. ''I made the final of the U.S. Open but lost to my friend Sloane Stephens. Right now I'm only thinking about the quarterfinals but hopefully big things can happen here.''
Later on Lenglen, Australian Open champion Caroline Wozniacki - seeded second - had a tough-looking fourth-round match against Daria Kasatkina. The 14th-seeded Russian has beaten her twice this year.