MELBOURNE —If Rafael Nadal wanted a fitness test in the first week of the Australian Open, he got one in his almost four-hour, 6-3, 6-7 (4), 6-3, 6-3 win over Diego Schwartzman.

No. 3-ranked Grigor Dimitrov did it tough, too, before advancing to the quarterfinals at the expense of the last Aussie in the draw. Dimitrov avenged a loss two weeks ago to Nick Kyrgios with a 7-6 (3), 7-6 (4), 4-6, 7-6 (4) win over Nick Kyrgios Sunday night.

He’ll next face Kyle Edmund, who reached his first Grand Slam quarterfinal with a 6-7 (4), 7-5, 6-2, 6-3 win over Andreas Seppi earlier in the afternoon and could relax and watch the night-time entertainment.

Nadal, with his spot in a 10th Australian Open quarterfinal secure, draped an arm around his Argentine friend Schwartzman and patted him on top of the head after they met at the net.

“A great battle ... he’s a good friend of mine,” Nadal said. “This is the first big match that I played in 2018. That’s confidence for myself ... confidence I can resist for four hours on court at a good intensity.”

Nadal lost last year’s Australian Open final to Roger Federer, but went on to regain the No. 1 ranking and win the French and US Open titles before bringing his season to a premature end because of an injured right knee.

He didn’t play a competitive match before the season-opening major, and advanced through three rounds without dropping a set.

That streak finished when Schwartzman took the second set, rebounding three times after dropping serve to break back against Nadal and level the match.

Nadal lifted to win the third, but Schwatzman didn’t relent.

The second game of the fourth set lasted almost 13 minutes and 20 points, with Nadal finally holding after saving five break points.

The 16-time major winner broke again in the next game and withstood more break points - seven in all in the last set and 15 of 18 in the match - before clinching it in 3 hours, 51 minutes.

“It was a good test for me. It was a lot of hours on court. Moments under pressure,” Nadal said. “So, yeah, a lot of positive things that I managed well.”

Nadal will next play 2014 US Open champion Marin Cilic, who collected his 100th Grand Slam match win with a 6-7 (2), 6-3, 7-6 (0), 7-6 (3) victory over No. 10 Pablo Carreno Busta.

“I had the 300th win of my career at the US Open in 2014, so this is also beautiful one,” Cilic said of his latest major milestone. “I hope I’m going to continue and gather three more here.”

Caroline Wozniacki continued to cash in on her second chance, reaching the quarterfinals here for the first time since 2012 with a 6-3, 6-0 win over Magdalena Rybarikova.

After saving match points and coming back from 5-1 down in the third set of her second-round win, No. 2-ranked Wozniacki said she was “playing with the house money” and had nothing to lose.

“I played really well from being down 5-1 ... since then I’ve just kept that going,” she said.

After a tight tussle in the opening four games against No. 19-seeded Rybarikova, a Wimbledon semifinalist last year, Wozniacki dominated the fourth-round match and conceded only six points in the second set. She tried a between-the-legs shot for the first time in a tour-level match.

“I think you can tell my confidence is high,” Wozniacki said in an on-court TV interview. “I tried a tweener today and it went in.”

Wozniacki next plays Carla Suarez Navarro, who came back from a set and 4-1 down to beat No. 32 Anett Kontaveit 4-6, 6-4, 8-6.

Elise Mertens reached the quarterfinals in her Australian Open debut, beating Petra Martic 7-6 (5), 7-5 to extend her winning streak to nine matches including a title run at the Hobart International. — AP