MELBOURNE, Australia -- Rafael Nadal struggled for nearly four hours on Sunday to grind out a 6-3, 6-7 (4-7), 6-3, 6-3 defeat of Argentine Diego Schwartzman and reach the Australian Open quarterfinals for the 10th time.
2009 winner Nadal, who has also lost three other finals at Melbourne Park, played the longest match of the tournament so far as he beat Schwartzman, one of the smallest on the tour.
Third seed Grigor Dimitrov meanwhile withstood 36 aces from Nick Kyrgios in a match which featured nearly 140 combined winners, with the Bulgarian pulling out a 7-6 (7-3), 7-6 (7-4), 4-6, 7-6 (7-4) victory.
Dimitrov, who lost to the Australian this month in the Brisbane semis, was broken as he served for the match leading 5-4 in the fourth set, with the encounter leading to a tiebreaker.
In the decider, the seed finally took command as an easy volley winner yielded three match points, with Dimitrov converting on his second, an untouchable volley.
"What can I say, playing Nick is tricky," Dimitrov said, "It was one of those matches where you have to be locked in and take any opportunities you have. Even when I was serving for the match, I didn't feel it was over, I'm just glad to get through it."
Dimitrov will be bidding for his second straight Melbourne semifinal when he plays Kyle Edmund, the new British tournament hope in the injury absence of Andy Murray.
Edmund exceeded expectations with his first quarterfinal berth at the majors, 6-7 (4-7), 7-5, 6-2, 6-3 over Italy's Andreas Seppi.
The Brit came from a set and a break down, winning with 25 aces as part of 63 winners.
Nadal, with 16 Grand Slam honors to his name, lost his first set of the week to the South American, aa Schwartzman saved two match points before going down to the Spaniard who will hold onto his number one ATP ranking by the end of the event on January 28.
"I built confidence for myself, knowing that I can resist almost four hours on court at a good intensity. I'm very happy for that," Nadal said. "It's always better winning in two hours than in four. It was a good test for me. It was a lot of hours on court, moments under pressure.
"There were a lot of positive things that I managed well. After the second set, it was a very tough moment. The third set was a great set to win.
"In the third and fourth my serve started working better, and probably that's why I am here with a victory."
The Spanish top seed will next test himself against 2017 Wimbledon finalist Marin Cilic, who won his 100th match at a Grand Slam against 10th seed Pablo Carreno Busta, 6-7 (2-7), 6-3, 7-6 (7-0), 7-6 (7-3) with 20 aces over nearly three and a half hours.
"It was up and down a lot, a difficult match," the Croatian said. "Conditions were a little bit more humid than before. Pablo was playing really good, very solid, and served really good today."
Women's second seed Caroline Wozniacki reached the last eight for the first time in six years with a 6-3, 6-0 defeat of Magdalena Rybarikova.
Wozniacki takes a 4-2 WTA-level record into her next match with Carla Suarez Navarro. Suarez Navarro turned in a heroic effort on Sunday, fighting back from a set and 4-1 down to overhaul Estonian Anett Kontaveit, 4-6, 6-4, 8-6.
Spain's world No. 39 swept the last five games of the second set to pull herself back into the fight, advancing to her sixth Grand Slam quarterfinal and third in Melbourne.
"I've played Caroline a lot of times," Suarez Navarro said. "It will be a really tough match. She's fighting every ball, but at the same time she can play aggressive. She has a lot of experience in these rounds."
Wozniacki took just 63 minutes to advance over Rybarikova, finishing with 25 winners as she won 11 of the last 12 games.
"I felt good about my game," Wozniacki said. "I'm in a good place, I'm hitting the ball well. Everything has been going well the last year and a half or so. It's been good."
Belgian Els Mertens, who missed a chance to play qualifying a year ago, finds herself in the last eight through a defeat of Croatian Petra Martic, 7-6 (7-5), 7-5.
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