PIX: Wawrinka rallies to beat Medvedev; Thiem cruises

Images from Day 8 of the 2020 Australian Open in Melbourne on Monday.

Former champion Stan Wawrinka battled past Russian fourth seed Daniil Medvedev in five sets to reach the Australian Open quarter-finals with a 6-2, 2-6, 4-6, 7-6(2), 6-2 victory on Monday.

Medvedev came into the contest having won both their career meetings at Grand Slams in four sets but the 2014 Australian Open champion took the opening set with a double break of the Russian's serve.

Medvedev, who lost to Rafa Nadal in five sets in last year's U.S. Open final, levelled the contest by breaking Wawrinka twice in the second and nosed ahead in the match with a break in the seventh game of the third.

But Wawrinka refused to yield and took the fourth set tiebreaker comfortably before breaking Medvedev twice in the fifth to set up a quarter-final against either German seventh seed Alexander Zverev or 17th seed Andrey Rublev of Russia.

Thiem sails past Monfils

Fifth seed Dominic Thiem kept his flawless record against Gael Monfils intact with a trouble-free 6-2, 6-4, 6-4 victory on Monday to reach his maiden Australian Open quarter-final.

Thiem, twice a French Open finalist, came into the fourth-round clash against the 10th seed having won all five of the matches they have previously played and did not face a single breakpoint against the Frenchman on the Rod Laver Arena.

"I think that I played my best match so far of this Australian Open. A very, very good feeling," the Austrian said.

"The score looks way easier than the match was. I think I was lucky to make an early break in each set and then was managing to hold my serve well. I'm so happy because I'm for the first time in the quarter-finals here."

Thiem, who lost to Rafael Nadal both times in the title match at Roland Garros, converted four of his 14 breakpoint chances and hit 31 winners to seal the contest.

Monfils surprised Thiem with an underarm serve in the second set, which the Austrian was unable to return, but the world number five managed to chase down most of the drop shots that the Frenchman employed against him.

"I always played my best tennis against him, so maybe that's one reason," Thiem said of his 6-0 record against Monfils.

The 26-year-old will meet the winner of the blockbuster clash between top seed Nadal and local hope Nick Kyrgios, seeded 23rd, for a place in the semi-finals.

It will be the first singles meeting between the Spaniard and Kyrgios since last year's Wimbledon when the temperamental Australian, who had previously described Nadal as a sore loser and "super salty", lost in four sets.

Thiem, who also confirmed that since last year his mother has been getting a tattoo every time he wins a tournament, was keen to watch the contest between his potential next opponents.

"I couldn't be happier to be done, to be in the quarter-finals and to watch that, relax from home. I'm also very excited for that match," Thiem said.

"Obviously it's going to be such an entertaining contest tonight and then also in two days, it doesn't matter who I face.

"So I'm really excited to watch that match and may the better one win tonight."

Halep beats Mertens to advance

Simona Halep had to be at her counter-punching best to see off a determined second-set comeback from Elise Mertens on Monday as the Romanian world number three advanced to the quarter-finals of the Australian Open with a 6-4, 6-4 victory.

Halep, a beaten finalist at Melbourne Park two years ago, will next meet either Estonia's 28th-seed Anett Kontaveit or Poland's Iga Swiatek in the last eight.

Mertens, who beat Halep in the Doha final last year, blasted bags of winners but also made 38 unforced errors as Halep chased down every ball and made the Belgian work for every point.

Mertens stormed back from a double break 3-0 deficit in the second set to level at 4-4, only for Halep to break in a marathon ninth game and serve out to advance to the last eight.

"Against her in Doha in the final I was leading a set and 4-2 and lost the match so I knew I had to stay focused until the end," two-time Grand Slam champion Halep said.

"To be honest I got a bit nervous at 4-3 (in the second).

"I had to calm down because when I get nervous I get a bit crazy on court so I had to stay cool and get energy from the box and not think (about the past).

"But I was strong enough to finish the match."

The pair broke each other once in the first eight games as they engaged in lengthy rallies of high quality shot-making.

The Romanian, however, managed to crack Mertens in the crucial ninth game when she jumped on a double fault at 15-30 and then sealed her second break with a forehand winner that allowed her to serve out in the 10th game.

Halep broke in the first game of the second set and while Mertens put her under all sorts of pressure in the next game, the fourth seed managed to scramble and keep the rallies alive.

But the Belgian finally got some traction when she got a break back and then held serve to get back to 3-2, conceding just one point in the two games.

She broke again in the eighth game as a frustrated Halep remonstrated with her box and whacked her racquet into the ground without breaking it.

That outburst seemed to help as she put Mertens under intense pressure in the 11-minute ninth game, which she took on her fifth break point opportunity, then sealed the win on her next service game.

Muguruza powers past Bertens into last eight

Garbine Muguruza powered into the Australian Open quarter-finals with a 6-3, 6-3 demolition of ninth-seed Kiki Bertens in just 68 minutes on Monday.

Muguruza, a former French Open and Wimbledon champion, was unseeded at Melbourne Park and has proved a dangerous floater in the draw, having also thrashed fifth seed Elina Svitolina 6-1 6-2 in the previous round.

The 26-year-old Spaniard, who was rusty before the tournament after withdrawing from Hobart with a virus and then lost the first set of her first round clash with Shelby Rogers 6-0, was almost unstoppable on Monday.

She broke Bertens five times throughout the match, including in the final game, and clinched a quarter-final with Anastasia Pavlyuchenkova when she blasted a forehand winner down the line.

Pavlyuchenkova ousts former champion Kerber to reach quarters

Russian Anastasia Pavlyuchenkova stayed brave in the face of a spirited fightback from former champion Angelique Kerber to move into the quarter-finals of the Australian Open with a 6-7(5), 7-6(4), 6-2 win.

German 17th seed Kerber rallied from 5-2 down and a 3-0 deficit in the tiebreaker to win the opening set against Pavlyuchenkova, who hit an incredible 28 winners to 12 unforced errors but still found herself trailing in the match.

The second set had a similar pattern as three-time Grand Slam winner Kerber saved three set points

to force a tiebreaker but the Russian 30th seed would not let the chance slip this time and levelled the match with a booming backhand winner.

Kerber finally ran out of gas as Pavlyuchenkova broke the 2016 winner three times in the decider and will next meet former French Open and Wimbledon champion Garbine Muguruza, who beat Kiki Bertens 6-3, 6-3 earlier on Monday.

Kontaveit holds off teenager Swiatek to reach last eight

Anett Kontaveit fought off a spirited challenge from Polish teenager Iga Swiatek to reach her first Grand Slam quarter-final with a 6-7(4), 7-5, 7-5 victory in the fourth round of the Australian Open on Monday.

The Estonian 28th seed saved 12 break points in a see-saw contest on Melbourne Arena as she battled back from a set down to book a last eight meeting with twice Grand Slam champion Simona Halep.

After losing the first set on a tiebreak, 24-year-old Kontaveit twice rallied from a break down to win the second set before racing to a 3-0 lead in the decider.

Swiatek, who mixed 42 winners with 51 unforced errors as she looked to become the youngest quarter-finalist at Melbourne Park since 2007, was not done yet, however.

The 18-year-old showed true grit to get the set back on serve at 5-5 and the match looked destined to be decided in a super tiebreak.

Kontaveit held her nerve and her serve, however, and sealed her place in the quarter-finals with her ninth break of the contest when the tough young Pole hit a backhand return wide.

"I couldn't be happier, it was such a battle today but so happy I stuck it out," said Kontaveit, who slumped to 31st in the world after a viral illness cut short her 2019 season.

"I'm very happy to be in the quarter-finals for the first time. I'm still shaking. I was just trying to stay as tough as I could and focus on every point."

Kontaveit has only played Halep twice, back in 2017 when the former Wimbledon and French Open champion first topped the world rankings.

The Estonian lost the matches in Rome and Miami in straight sets and knows she will have her work cut out against the fourth seed in Melbourne.

"Simona's so tough so I'll probably have to do everything well," she said.

"I have nothing to lose so I'll just go out and give it my all."