Novak Djokovic survived a scare to join Roger Federer and Serena Williams in the Australian Open second round as heavy downpours caused chaos on Monday, forcing organisers to postpone a swathe of matches.

Defending champion Djokovic was made to sweat before beating Germany’s Jan-Lennard Struff in four sets on the first day, when fears over air pollution were replaced by disruption caused by rain.

While play continued at the three stadiums with retractable roofs, half of the 64 scheduled matches were postponed, ensuring a big backlog for Tuesday.

Wet conditions are unusual for the Australian Open, which is more used to extreme heat and was plagued by smog from bushfires during qualifying, when players suffered coughing fits and breathing problems.

Air quality was rated ‘good’ as the first round started on Monday but about four hours later play was suspended on outside courts when the heavens opened in Melbourne.

World number three Federer was briefly hauled off court while the roof was closed on Rod Laver Arena before returning to complete a routine 6-3, 6-2, 6-2 victory over American Steve Johnson.

Williams, on the hunt for a record-equalling 24th Grand Slam title, won the first set against Anastasia Potapova in just 19 minutes as she cruised to a 6-0, 6-3 win in less than an hour.

“I feel like I can still improve and get better throughout this tournament, for sure. This is a good stepping stone for right now,” Williams said.

However, Williams’ elder sister Venus was ousted in stunning fashion by 15-year-old Coco Gauff, who won 7-6 (7/5), 6-3 in a repeat of her first-round upset at Wimbledon last year.

In the late match, defending champion Djokovic dropped his first set since 2006 in the opening round before recovering to beat Jan-Lennard Struff 7-6 (7/5), 6-2, 2-6, 6-1.

“There is a lot of pressure and a lot of different emotions involved. I definitely try to remind myself to stay present and really enjoy,” said the seven-time Melbourne winner, who brought up his 900th Tour-level victory.

Former US Open champion Sloane Stephens was the biggest women’s casualty on day one when she crashed out in three sets to Zhang Shuai of China – her fourth first-round exit in Melbourne.

Shapovalov racquet row

Defending champion Naomi Osaka was done well before the downpour as she dismissed Marie Bouzkova of the Czech Republic 6-2, 6-4 in 80 minutes, smashing one powerful serve that broke a net fastening.

“It was really tough for me trying to control my nerves,” said Osaka. “It’s tough to play someone you’ve never played before in the first round of a Grand Slam.”

Later on the covered centre court, Australian world number one Ashleigh Barty recovered strongly from a set down to beat Lesia Tsurenko 5-7, 6-1, 6-1.

In the men’s draw, Greek sixth seed Stefanos Tsitsipas, who beat Federer en route to last year’s semis, crushed Salvatore Caruso 6-0, 6-2, 6-3.

Player anger over smog dominated the final days before the tournament, which is taking place after bushfires ravaged large parts of Australia, destroying thousands of homes and killing 29 people.

Tournament officials are closely monitoring pollution and will halt play and close the three main stadiums’ roofs if particulate matter suspended in the air hits PM2.5 200.

In other results, Canadian 13th seed Denis Shapovalov argued furiously with the umpire over a code violation for throwing his racquet as he lost in four sets to Marton Fucsovics.

Croatian 25th seed Borna Coric was another first-round loser as he went down to experienced American Sam Querrey, while Australia’s Sam Stosur bombed out against Caty McNally.

But former champion Caroline Wozniacki, playing her last tournament before retiring, safely reached the second round as she beat Kristie Ahn 6-1, 6-3.

Nadal insists beating Federer’s 20 Slams not important

World number one Rafael Nadal insisted Tuesday that matching or beating Roger Federer’s record 20 Grand Slam titles is not important and he was “super happy” with his tennis career regardless.

The Spaniard launched his campaign to equal the Swiss great’s mark by dropping just five games in a 6-2, 6-3, 6-0 annihilation of Bolivian Hugo Dellien in the Australian Open first round.

The Mallorcan, the first man to be world number one in three different decades, can not only match his great rival’s achievement, but also become the first man in the Open era to win all four Majors at least twice if he lifts the trophy again at Melbourne Park.

It is a big ask for the 33-year-old Nadal, who has only won the title once before in Australia, against a tearful Federer in 2009, with four runner-up finishes to his name.

“I don’t care about 20 or 15 or 16. I just care about trying to keep going, keep enjoying my tennis career,” said Nadal.

“It’s not like 20 is the number that I need to reach. If I reach 20, fantastic. If I reach 21, better. If I reach 19, super happy about all the things that I did in my tennis career.

“I am very satisfied about my tennis career because I give it all most of the time,” he added. “That’s the only thing that matters.”

The Australian Open is the only Major Nadal has failed to win more than once, having claimed 12 titles at Roland Garros, four at the US Open and two at Wimbledon.

He has been a finalist in Melbourne four times since winning but has struggled to get over the line, something that baffles him.

“I have been a break up twice in the fifth set and I lost. Another time I have been injured in a final, of course, against a great opponent,” he said on why he had not been able to convert in Australia.

Main goal

Nadal, in a pink sleeveless shirt and matching shoes, was in total charge against the world number 73 Dellien, storming to a 5-0 lead in the opening set before the Bolivian held serve, then against the odds broke, before the Spaniard served out the set.

Underdog Dellien was broken in the sixth game of the second set but hit back again to break Nadal for the second time in the match before the top seed again rallied to restore control with some sizzling forehands down the line.

Nadal raced 3-0 up in the third set as his physicality and power shone through.

The Spaniard next plays either Argentine Federico Delbonis or Portugal’s Joao Sousa and said he never looked further ahead than the next match.

“I think about Sousa or Delbonis, that’s all. I think about my practice tomorrow, try to follow up the level of tennis that I played in the third set,” he said.

“That should be my main goal. I need to play at my highest level if I want to keep going in the tournament.

“If I am able to reach my highest level, that’s the thing that I have to worry about.

“If I am able to play at my highest level, normally I am able to produce some good chances.

“If not, impossible.”