Defending champion Aryna Sabalenka extended her Australian Open winning streak to 15 matches on a rain-soaked opening day at Melbourne Park.

Less than an hour of play was possible on the outside courts before a huge thunderstorm hit Melbourne Park, sending spectators running for cover and causing a delay of more than six hours.

The matches continued as scheduled on the three covered courts, and Sabalenka opened the night session on Rod Laver Arena with a 6-3 6-2 victory over former US Open champion Sloane Stephens.

While it was a tough draw on paper, Stephens has slipped to 81 in the rankings and, barring a mini revival from the American when she won three games in a row after losing the first four, this was smooth sailing for Sabalenka.

The two-time champion said: “It was a tough match, always tough matches against her. Not that I played my best probably but I was glad I was able to close this match in straight sets.”

The player Sabalenka beat in the final last year, fifth seed Zheng Qinwen, also safely reached round two.

The 22-year-old from China, who went on to win Olympic gold in Paris, did not have things all her own way against Romanian qualifier Anca Todoni but battled to a 7-6 (3) 6-1 victory.

Zheng looked in complete control serving for the set at 5-4 and leading 40-0 only for Todoni to win five points in a row.

The Romanian then held three set points with Zheng serving at 5-6 but could not take any of them and things were comfortable for the fifth seed thereafter.

“The first match is always not easy,” said Zheng in her on-court interview. “She’s playing really good but I was doing a bit stupid mistakes at 5-4 40-0, I don’t know what happened there.”

Teenager Mirra Andreeva could be a factor come the latter stages of the tournament and she began strongly with a 6-3 6-3 victory over Marie Bouzkova.

But 29th seed Linda Noskova, who upset Iga Swiatek on her way to the quarter-finals last year, fell to a 5-7 6-3 6-4 loss against talented Dane Clara Tauson.

In the men’s singles, sixth seed Casper Ruud survived a major scare to avoid a first opening-round loss at a grand slam since Wimbledon four years ago.

The Norwegian was twice pegged back by Spaniard Jaume Munar but proved too strong in the deciding set to claim a 6-3 1-6 7-5 2-6 6-1 victory.

Also prevailing in a fifth was Japanese veteran Kei Nishikori, who came from two sets down to beat Brazil’s Thiago Monteiro 4-6 6-7 (4) 7-5 6-2 6-3 for just his second slam victory since 2021.

The 35-year-old former US Open finalist has been dogged by injuries in recent years but, after saving two match points in the third, he extended his five-set record to a superb 29 wins from 37 matches, coming through in four hours and six minutes.

Nishikori has quite the reputation for winning in matches that go the distance, and he said: “Even after the match, everybody, a couple of players, was joking to me, ‘Another five sets’.

“I mean, it’s good to have that record because I always have good confidence, and players know that I have a good record. It’s good pressure for them if I have that.”

Second seed Alexander Zverev played the final match of the night session and he eased to a 6-4 6-4 6-4 win over France’s Lucas Pouille.