MELBOURNE — Roger Federer showed his full championship form, but Stan Wawrinka was felled by a post-surgery knee as the former Australian Open champions split the difference in the second round on Thursday.
The pair got lucky from a weather standpoint, playing cooler (88-degree) night matches after 104-degree summer daytime temperatures.
Federer, in the hunt for a sixth Melbourne title and 20th Grand Slam singles title, won 6-4, 6-4, 7-6 (7-4) against German Jan-Lennard Struff.
But 2014 Melbourne winner Wawrinka showed that he still needs more recovery time after his summer knee operation, falling to American Tennys Sandgren 6-2, 6-1, 6-4 in 88 minutes with 35 unforced errors.
“I was struggling with everything, not the knee especially, the knee was still handling well,” said Wawrinka, a three-time Grand Slam winner.
“As long as I enter on the court, and I don’t feel any big injury, I’m not going to retire (from a match). I was here to fight and to try everything I could.”
Federer played and won his 102nd Australian Open match and is one of two men — Jimmy Connors is the other — to have played at least 100 matches at any Grand Slam event.
Federer’s only wobble came as he went down a break in the third set, getting it back for 3-all with a clean passing winner.
But he did have to clinch it in a tiebreaker, firing a service winner to close out victory.
“I’ve trained with him and played him so I had the information on his game,” Federer said. “I knew he would go for his shots.
“I focused on protecting my serve. It was not an easy match, I enjoyed it.”
Federer takes a 16-2 record over Richard Gasquet into his third-round match.
Six-time champion Novak Djokovic showed iron-man stamina as he battled hothouse conditions to overcome fatigued Frenchman Gael Monfils 4-6, 6-3, 6-1, 6-3.
Djokovic, seeded 14th after not playing since Wimbledon due to an elbow injury, is showing that his comeback after six inactive months is starting to take flight. He advanced with 31 winners and seven breaks of serve.
But Djokovic is still dealing with his injury, which he admits is not yet perfect.
“It’s still not 100 percent, but building,” the 31-year-old said. “I have a lot of faith and self-belief. I know what I’m capable of. This is the most successful court of my career.”
The contest featured several momentum shifts as both men battled the scorching heat.
Monfils said he felt dizzy and faint at some points, but had to play on as umpires enforced the role of 25 seconds only between points.
“No matter how much you train in the heat, how much you like the heat, is very tough. It was a tough decision I think for the official. It’s a little bit hot, maybe a little bit too hot.”
German fourth seed Alexander Zverev defeated compatriot Peter Gojowczyk 6-1, 6-3, 4-6, 6-3.
Austrian fifth-seed Dominic Thiem made his second career recovery from two sets to love down to topple American qualifier Denis Kudla, 6-7 (6-8), 3-6, 6-3, 6-2, 6-3.
Frenchman Julien Benneteau stunned seventh seeded Belgian David Goffin 1-6, 7-6 (7-5), 6-1, 7-6 (7-4); 12th-seeded Juan Martin del Potro got injury treatment on a hip, but defeated young Russian Karen Khachanov 6-4, 7-6 (7-4), 6-7 (0-7), 6-4.
On the women’s side, Taiwan’s Hsieh Su-Wei claimed the biggest upset so far at the Australian Open, knocking out third-seed Garbine Muguruza 7-6 (7-1), 6-4 in the second round in draining heatwave conditions.
Top-seed Simona Halep successfully tested an injured ankle under match conditions, producing a 6-2, 6-2 defeat of Canadian Eugenie Bouchard.
Halep rolled the ankle in her first-round win and was unsure of playing before making the call to go ahead.
“I still feel pain, and I couldn’t practice much,” she said. “But during the match, I just forgot about it. I had a very tight tape.
“The most important thing is that I could play my game not thinking about the ankle. I did that great today.”
Reigning Wimbledon champion Muguruza came to the court with lingering fitness problems after cramping in matches in recent weeks, calling for her trainer as she faced the 88th-ranked Hsieh, a former doubles No. 1.
The problem turned out to be heat-related.
“It’s blisters at the end, I think the surface of the court,” Muguruza said. “I don’t know how much heat, it’s terrible, very, very hot, and it’s easy to get blisters.
“My foot was already wrapped, but very quickly I started to feel a blister was coming. I’d rather prevent than having the problem after.
“I’ve had tougher matches under the heat previous years in Australian Open, today was hot, but I don’t think was the hottest day.”
Muguruza came from 2-5 down in the opening set but ended up losing it in a tiebreaker. In the second, she saved a match point to hold for 4-5 but was beaten a game later as Hsieh put a backhand winner out of reach in the far corner.
The demanding conditions proved too much for another seeded player. British No. 9 Johanna Konta, a 2016 semifinalist, lost 6-4, 7-5 to 123rd-ranked Croatian-born Bernarda Pera of the U.S.
Maria Sharapova went through in straight sets to reach the third round with a defeat of Latvian 14th-seed Anastasija Sevastova 6-1, 7-6 (7-4).
The Russian worked for 80 minutes on Rod Laver Arena to secure victory, saving herself from a third set with a winning tiebreak effort to close out the match.
French eighth-seed Caroline Garcia advanced past Czech Marketa Vondrousova 6-7 (3-7), 6-2, 8-6, while Agnieszka Radwanska beat Lesia Tsurenko 2-6, 7-5, 6-3 and Barbora Strycova stopped Spain’s Lara Arruabarrena 6-3, 6-4.
2016 winner Angelique Kerber continued her fast start to 2018, winning her 11th match since the start of the year over Donna Vekic 6-4, 6-1.
U.S. Open finalist Madison Keys took her post-New York record to 2-2 as she put out Russian Ekaterina Alexandrova 6-0, 6-1.