Sharapova, Nishikori win under cover as rain wreaks havoc at the Australian Open

Unseasonal and relentless Melbourne rain has played havoc on Day 5 of the Australian Open, with play not even managing to get underway on any outside courts during the day session.

Despite the delays in the outer, play did resume on time under roofs of the three main courts, with Japan's Kei Nishikori the first to advance undercover at Margaret Court Arena.

The seventh seed shook off a willing challenge from Spain's Guillermo Garcia-Lopez, who dominated Nishikori in the second set, however Japan's no. 1 player managed to regain the upper hand in the third and fourth sets, winning 7-5, 2-6, 6-3, 6-4.

Nishikori told the press he had to shake off his niggling wrist injury to take control in the third set.

"I had (the injury) two years ago... maybe it has come back a little bit, but it should be okay for the next match," Nishikori said.

"I have to give credit to (Garcia-Lopez), he was hitting hard, really flat balls that were tough to play.

"I tried to dictate a little more, step in and use more forehands, and I think it was working."

On the women's side of the draw, fifth seed Maria Sharapova flexed her muscle in a three set win against the USA's Lauren Davis.

Sharapova squandered an opportunity to wrap the match up in a second set tiebreak, but stepped up a gear in the third to eventually win 6-1, 6-7, 6-0.

The win means the 2008 Australian Open winner sets up a fourth round showdown with Swiss young gun Belinda Bencic. The Russian player said Bencic was an "inspired player" who was rising up the ranks quickly.

"It's going to be a tough one," Sharapova said, "she's been playing incredibly well, especially last season. I'm just going to do everything I can to win."

Bencic survived a scare herself to advance to the fourth round, after Ukrainian Kateryna Bondarenko won the first set against the 12th seed in convincing fashion.

But the two-time junior Grand Slam winner managed to rally and force a third set, however, eventually winning 4-6, 6-2, 6-4 in just under two hours.

Despite guaranteeing herself a maiden final 32 result at the Australian Open, Bencic said there was room for improvement ahead of her match-up against Sharapova in two days' time.

"I still feel there can be a lot of improvement in my game and how I can play," Bencic said.

"But I'm happy I fought through even if it wasn't perfect. Tomorrow I can have a good doubles match and practice so I can play even better."

Meanwhile on Hisense arena Belgium's David Goffin won his way into the final 32 with a hard-fought four-set win over close friend and 19th seed Austrian Dominic Thiem.

Goffin, ranked 15th at the Open, said playing a friend was always difficult, as you had to prepare mentally as well as physically.

"It's always tough against Dominic, it was almost three hours of high-intensity tennis," Goffin said post-match.

"I'm really happy with the way I managed the match emotionally as it is tough to play a friend."

Goffin will play ninth seed Frenchman Jo-Wilfried Tsonga after he cruised past compatriot Pierre-Hugues Herbet in straight sets, 6-4, 7-6, 7-6, while in an upset late in the day session, 13th seed Roberta Vinci joined 18 other women's seeds on the loser's list, going down to Anna-Lena Friedsam of Germany in three sets.

With play on outside courts delayed due to the rain, a number of doubles matches were cancelled throughout the day, while a number of singles matches scheduled for an 11am start were still yet to begin.

The night session continues in Melbourne on Friday night, with Serena Williams, Novak Djokovic and local hopes Daria Gavrilova and Nick Kyrgios all scheduled to play. Endit