Shang Juncheng of China plays a forehand return to Mackenzie McDonald of the US during their Australian Open first-round match at Melbourne Park, Melbourne, Australia, on Tuesday. Shang won in five sets, 6-3, 1-6, 3-6, 6-4, 6-2. AP

In pulling off a five-set opening win in Melbourne to match his best record at the Australian Open, teen star Shang Juncheng has added fuel to the early-season surge of the Chinese men.

Outsized and overpowered by most of his opponents on the men's pro circuit, Shang proved again that resilience and endurance can also prevail in the physically demanding sport. After stunning American world No 42 Mackenzie McDonald, 6-3, 1-6, 3-6, 6-4, 6-2, in his main draw opener on Tuesday, Shang has reached the second round at Melbourne Park for a second consecutive year.

With Shang's senior compatriot Zhang Zhizhen having already advanced on Monday, this year's Aussie Open marks the first time in history that two Chinese men have fought their way into the second round at the season opening Grand Slam main draw, cementing a long-awaited rise to the top of the sport for the nation's male players after decades of underachieving.

Ranked 140th this week, the 18-year-old Shang showed a strength of will, consistency and tenacity beyond his years, as he came back from 2-1 down to upset McDonald in a physically grueling three-and-a-half-hour battle to avenge his loss to the same opponent at an ATP 250 tournament in Zhuhai, Guangdong province, in September.

Shang's impressive result Down Under builds on his career first semifinal berth on the ATP circuit two weeks ago at the Hong Kong Open, where he clinched two of his three wins in the deciding set, before losing to world No 5 Andrey Rublev in a three-set battle.

Shang attributed his much-improved composure and consistency in long-haul matches to a solid offseason training program focusing on diet and conditioning.

"Physically I feel refreshed and ready to fight after I changed what I eat and how I approach my fitness training a little bit in the offseason. I've adopted a low-carb diet and I did more aerobics than weight training, which has helped me a lot," Shang said before the Australian Open.

Leading the Chinese men's charge into the tournament's second week alongside Shang is the country's top-ranked Zhang, who is also riding a wave of early-season momentum in Australia to push for more breakthroughs following a year of growth in 2023.

"I think I am more confident now facing players ranked lower than me, and I have a better understanding of my strengths and weaknesses when challenging higher-ranked opponents," Zhang, ranked 54th, said after beating Argentinian Federico Coria in straight sets on Monday.

Facing world No 21 Ugo Humbert in the second round, Zhang shrugs off any pressure as an underdog against the Frenchman.

"Hopefully I can maintain my form and earn more points during the early stage of the season to try and break into the top 30 this year," said Zhang, who became the first male Chinese mainland player to crack the top 100 in October 2022.

'Queen' Wen holds court

On a relatively disappointing day for the Chinese women, the country's top ace Zheng Qinwen held her nerve to come back from a set down and secure an opening-round win against Ashlyn Krueger, 3-6, 6-2,6-3, at the Kia Arena.

By Tuesday afternoon, before Zheng's match, five of the seven Chinese contenders in the women's draw had crashed out, with Zheng's victory, and another three-set win from veteran Wang Yafan, serving up some solace for Chinese fans.

As the WTA's Most Improved Player in 2023, Zheng, who was nicknamed "Queen Wen" by fans for her powerful forehand shots, started slowly against an aggressive Krueger, hitting seven double faults in the first set. However, she found her serve and pace in time to outplay the American world No 78, cheered on by a fervent Chinese contingent in the crowd.

"She is really a good player and her strong serve was difficult for me. I started feeling better and better in the second set. I am really happy to play here and win my first round match, even though I faced difficulty," said Zheng, the current world No 15.

"I always believe anything can happen. I try to not put too much pressure on myself and I don't look too far ahead, instead, I just focus on the moment and try to enjoy playing tennis in Melbourne."

Swiatek rallies for win

Top-ranked Iga Swiatek survived an early test of her Australian Open title hopes when she beat former champion Sofia Kenin 7-6 (2), 6-2 in the first round on Tuesday.

Kenin, tournament winner in 2020, served for the first set at 5-4, but could not close it out and Swiatek took it in the tiebreaker. The No 1 seed then broke Kenin in the fifth game of the second set and held on to clinch victory.

"I'm really happy," said Swiatek. "It wasn't easy to find my rhythm. I felt a little bit off, and Sofia did everything to keep it that way. Huge respect to her. But, I managed to get my level up in the second set."

The Polish player is trying to win her fifth Grand Slam title and her first in Melbourne.

She'll face another tough match in the second round against 2022 Australian Open runner-up Danielle Collins, who beat 2016 champion Angelique Kerber 6-2, 3-6, 6-1.

"It's a tough little bracket that we have!" Collins said of the first two rounds. "I was like, 'wow, I get really great draws now'. But, if you're trying to win a Grand Slam, you kind of have to beat everyone."

Kerber was one of three past Australian champions making their return to Melbourne Park for the first time as mothers.

She joined four-time major winner Naomi Osaka as a first-round exit. Caroline Wozniacki, the 2018 winner, has reached the second round.