Spain's Rafael Nadal celebrates after defeating Federico Delbonis of Argentina in their second round match at the Australian Open tennis championship in Melbourne, Australia, Jan 23, 2020. (DITA ALANGKARA / AP)

MELBOURNE - Rafael Nadal and Stanislas Wawrinka had their credentials tested on day four of the Australian Open on Wednesday, both overcoming surprise challenges to progress to round three.

Despite otherwise dominating the contest, Rafael Nadal looked like going to four sets before eventually reclaiming a firm grip on the match and winning 6-3, 7-6 (4), 6-1

Among those joining them were Simona Halep, Daniil Medvedev, Karolina Pliskova, Dominic Thiem and Nick Kyrgios.

Nadal was pushed to a second set tiebreak against Argentina's Federico Delbonis, after failing to clinch a break of his opponent's serve.

Despite otherwise dominating the contest, the legendary Spaniard looked like going to four sets before eventually reclaiming a firm grip on the match and winning 6-3, 7-6 (4), 6-1.

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"When you are not able to convert the break point after who knows how many chances, then of course you are in trouble," Nadal told Xinhua after the match.

"But I'm happy that I was able to play, I think a good tiebreak, to win that second set and then the third I think I played much better."

One of those who did go to a fourth, and then a fifth set, was Switzerland's three-time Grand Slam champion Wawrinka, who endured a surprise three and a half hour battle with Italy's Andreas Seppi, which ended 4-6, 7-5, 6-3, 3-6, 6-4.

Earlier, bad weather once again wreaked havoc with scheduling on the outdoor courts at Melbourne Park, with play starting late and some matches postponed.

This time it was dirty rain caused by lingering dust clouds above the city, forcing tournament workers to sweep muddy water from the outdoor courts before the matches could begin.

Under the protection of the stadium roof, fourth seed Medvedev of Russia progressed with relative ease, beating Spaniard Pedro Martinez 7-5, 6-1, 6-3.

Switzerland's Stan Wawrinka makes a backhand return to Italy's Andreas Seppi during their second round singles match at the Australian Open tennis championship in Melbourne, Australia, Jan 23, 2020. (ANDY BROWNBILL / AP)

In the women's draw, former World No 1 Simona Halep moved through to the next round despite a late fightback from her opponent Harriet Dart, with a final score of 6-2, 6-4. Dart was the final British singles player to depart the tournament.

Another former women's world No 1, Karolina Pliskova from the Czech Republic, also progressed to round three, beating Germany's Laura Siegemund 6-3, 6-3.

Colorful Australian Nick Kyrgios gave the home crowd something to cheer, beating Frenchman Gilles Simon, 6-2, 6-4, 4-6, 7-5.

Playing from two sets up, the controversial Australian decided to employ some of his trademark theatrics.

After receiving a questionable violation for taking too long to serve, Kyrgios responded by imitating Nadal's serving ritual, mimicking tucking his hair behind his ears, raising a smile from the umpire.

The theatrics proved unwise, however, with Kyrgios dropping the next set and bringing his victory into jeopardy.

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Despite the possibility of an embarrassing loss, Kyrgios once again served himself out of trouble, breaking Simon late in the third set and delivering two aces to seal the final game.

When asked about Kyrgios' impersonation of him, Nadal said that he had more important things to worry about.

"I really don't care," he said, "I'm here to play tennis."