Alexei Popyrin has underlined why he is a rising star of Australian tennis after comfortably progressing to the third round at Melbourne Park via a straight-sets win.

Key points: Alexei Popyrin did not drop a set in beating Jaume Munar to make his way into the third round of the Australian Open

Alexei Popyrin did not drop a set in beating Jaume Munar to make his way into the third round of the Australian Open Alex Bolt appeared on the verge of a massive upset before he lost in five sets to Dominic Thiem

Alex Bolt appeared on the verge of a massive upset before he lost in five sets to Dominic Thiem Ash Barty played first-round doubles match on her day off between singles commitments, winning alongside Julia Goerges

Popyrin exerted his command over Spain's Jaume Munar early in their Australian Open encounter on Court Three en route to winning 6-2, 7-6 (7/5), 6-2 in two hours and four minutes.

The win sees Popyrin equal his best showing at a major, 12 months after he reached the third round of the Open and was unlucky not to reach the last 16 when he lost to Frenchman Lucas Pouille in a memorable five-setter.

Popyrin's win followed a heroic performance from compatriot Alex Bolt, who had led fifth seed Dominic Thiem two sets to one before losing in five 6-2, 5-7, 6-7 (5/7), 6-1, 6-2 on Melbourne Arena.

Munar had few answers to Popyrin's arsenal of weapons, with the 20-year-old mixing up his game with his thunderous serve and heavy ground strokes.

He started brilliantly with consecutive aces from his opening two serves, while the former French Open junior champion clinched the first set with a powerful backhand passing shot that illustrated his strength off the left wing.

Six double faults and 34 unforced errors had the potential to blot his copybook, but the 96th-ranked Popyrin — whose lanky build fits around his 196-centimetre frame — never looked a chance of falling to his Spanish opponent.

Popyrin will enter the third round as the underdog against fourth seed and US Open finalist Daniil Medvedev, who earlier in the day produced a 7-5, 6-1, 6-3 win over qualifier Pedro Martinez.

Bolt pushes Thiem to the limit

Alex Bolt led Dominic Thiem two sets to one in their second-round match. ( AP: Lee Jin-man )

On paper, the 140th-ranked Bolt appeared to have little chance of beating two-time French Open finalist Thiem, who entered the Open as the world number five.

Day four results (men's draw) Daniil Medvedev (RUS, 4) def. Pedro Martinez (ESP) 7-5, 6-1, 6-3

Daniil Medvedev (RUS, 4) def. Pedro Martinez (ESP) 7-5, 6-1, 6-3 Dominic Thiem (AUT, 5) def. Alex Bolt (AUS) 6-2, 5-7, 6-7 (5/7), 6-1, 6-2

Dominic Thiem (AUT, 5) def. Alex Bolt (AUS) 6-2, 5-7, 6-7 (5/7), 6-1, 6-2 Alex Zverev (GER, 7) def. Egor Gerasimov (BEL) 7-6 (7/5), 6-4, 7-5

Alex Zverev (GER, 7) def. Egor Gerasimov (BEL) 7-6 (7/5), 6-4, 7-5 Gael Monfils (FRA, 10) def. Ivo Karlovic (CRO) 4-6, 7-6 (10/8), 6-4, 7-5

Gael Monfils (FRA, 10) def. Ivo Karlovic (CRO) 4-6, 7-6 (10/8), 6-4, 7-5 David Goffin (BEL, 11) def. Pierre-Hugues Herbert (FRA) 6-1, 6-4, 4-6, 1-6, 6-3

David Goffin (BEL, 11) def. Pierre-Hugues Herbert (FRA) 6-1, 6-4, 4-6, 1-6, 6-3 Stan Wawrinka (SUI, 15) def. Andreas Seppi (ITA) 4-6, 7-5, 6-3, 3-6, 6-4

Stan Wawrinka (SUI, 15) def. Andreas Seppi (ITA) 4-6, 7-5, 6-3, 3-6, 6-4 Karen Khachanov (RUS, 16) def. Mikael Ymer (SWE) 6-2, 2-6, 6-4, 3-6, 7-6 (10/8)

Karen Khachanov (RUS, 16) def. Mikael Ymer (SWE) 6-2, 2-6, 6-4, 3-6, 7-6 (10/8) Andrey Rublev (RUS, 17) def. Yuichi Sugita (JAP) 6-2, 6-3, 7-6 (7/5)

Andrey Rublev (RUS, 17) def. Yuichi Sugita (JAP) 6-2, 6-3, 7-6 (7/5) John Isner (USA, 19) def. Alejandro Tabilo (CHI) 6-4, 6-3, 6-3

But as the wildcard showed at the Australian Open last year — when he reached the third round —Bolt does not fear his opponents and he took the fight to Thiem in front of a parochial home crowd.

Thiem had raced through the first set in swift fashion and it appeared he was in for a straightforward afternoon, but Bolt had other ideas.

He knew he had nothing to lose and threw caution to the wind to level the match at one set apiece in the second, before he wrested control of proceedings from Thiem by taking the third in a tiebreak.

Thiem looked deflated at times during the second and third sets and with the crowd roaring on Bolt after every point won, an upset seemed to be brewing.

But Thiem found composure when it was needed most and after securing two breaks of the serve he secured the fourth set with relative ease.

His pressure on the Bolt serve was rewarded again with a double break in the fifth set, which paved the way for the 26-year-old to wrap up the win in three hours and 22 minutes.

Barty juggles doubles with singles in Melbourne

Most top-ranked players vying for the women's and men's singles titles at the Australian Open tend to use their days off between matches to rest up and recover.

But Ash Barty is keeping herself busy in her down time by playing doubles at Melbourne Park.

Ash Barty (left) has teamed up with Julia Goerges to play the doubles in Melbourne. ( AAP: Michael Dodge )

Barty will face Elena Rybakina in the third round of the singles on Friday and she warmed up for that clash by playing alongside German veteran Julia Goerges in the doubles this afternoon.

The duo made light work of Australian pair Jessica Moore and Astra Sharma to win 6-2, 6-3 under the roof on Melbourne Arena.

Day four results (women's draw) Karolina Pliskova (CZE, 2) def. Laura Siegemund (GER) 6-3, 6-3

Karolina Pliskova (CZE, 2) def. Laura Siegemund (GER) 6-3, 6-3 Simona Halep (ROU, 4) def. Harriet Dart (GBR) 6-2, 6-4

Simona Halep (ROU, 4) def. Harriet Dart (GBR) 6-2, 6-4 Belinda Bencic (SUI, 6) def. Jelena Ostapenko (LAT) 7-5, 7-5

Belinda Bencic (SUI, 6) def. Jelena Ostapenko (LAT) 7-5, 7-5 Kiki Bertens (NED, 9) def. Arina Rodionova (AUS) 6-3, 7-5

Kiki Bertens (NED, 9) def. Arina Rodionova (AUS) 6-3, 7-5 Elise Mertens (BEL, 16) def. Heather Watson (GBR) 6-3, 6-0

Elise Mertens (BEL, 16) def. Heather Watson (GBR) 6-3, 6-0 Angelique Kerber (GER, 17) def. Priscilla Hon (AUS) 6-3, 6-2

Angelique Kerber (GER, 17) def. Priscilla Hon (AUS) 6-3, 6-2 Donna Vekic (CRO, 19) def. Alize Cornet (FRA) 6-4, 6-2

Donna Vekic (CRO, 19) def. Alize Cornet (FRA) 6-4, 6-2 Catherine Bellis (US) def. Karolina Muchova (CZE, 20) 6-4, 6-4

Barty has been criticised in the past for trying to juggle her singles commitments with her doubles play at the majors.

She was forced to withdraw from the doubles at last year's Australian Open after the opening round because of an abdominal strain, yet that appeared to be a precautionary measure during her charge to the quarter-finals of the singles.

Barty's decision to play doubles this year is set to again become a talking point the deeper she goes in the singles draw in Melbourne, as she attempts to become the first local to win the women's championship in 42 years.

But the world number one has never shied away from contesting both draws at the majors and she even partnered Victoria Azarenka to make last year's US Open final when she was seeded second in the singles.

For Barty, playing doubles goes beyond what happens on the court.

"It is the relationships you build off the court and the friendships that are more important than tennis sometimes," Barty said after her win with Goerges.

Barty (R) and CoCo Vandeweghe show off the US Open women's doubles trophy in 2018. ( AP: Adam Hunger )

Barty has previously enjoyed success in doubles, having joined American CoCo Vandeweghe to win the US Open crown in 2018, while she has also achieved a career-high number five ranking.

She also reached the finals of the Australian Open (2013), the French Open (2017) and Wimbledon (2013) with countrywoman Casey Dellacqua.

Tomljanovic goes down swinging

Earlier, Barty's fellow Australian Ajla Tomljanovic fall short of advancing to the third round of the women's singles following a tight three-set loss to former world number one Garbine Muguruza.

Tomljanovic showed admirable character to force a third set against Muguruza, however the class of the two-time major winner shone through when it counted and she won 6-3, 3-6, 6-3 after two hours and 21 minutes on Rod Laver Arena.

Australia's Ajla Tomljanovic went down in three sets to Garbine Muguruza. ( AP: Dita Alangkara )

Barty is the only Australian to have advanced to the third round of the women's draw so far, with Priscilla Hon and Arina Rodionova joining Tomljanovic in departing the tournament.

Hon, a wildcard, lost in straight sets to 2016 champion and 17th seed, Angelique Kerber, 6-3, 6-2.

Rodionova, another Australian wildcard, went down to Dutch ninth seed Kiki Bertens 6-3, 7-5.