Roger Federer and Novak Djokovic both reached round four of the Australian Open with straight-set wins – although the Serb suffered an injury scare.

Switzerland’s five-time champion Federer beat Richard Gasquet 6-2 7-5 6-4 to progress to the last 16.

Six-time winner Djokovic had treatment on his lower back and leg but saw off Albert Ramos-Vinolas 6-2 6-3 6-3.

“It’s nothing major to be concerned about. It’s things that surface every day. I guess it’s normal,” he said.

Djokovic, 30, is playing in his first event since Wimbledon last year after a six-month lay-off with an elbow injury.

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Despite the convincing scoreline he was not at his best on Margaret Court Arena and was often frustrated on court.

However, he closed out the match in two hours, 23 minutes and progresses to face 21-year-old South Korean Hyeon Chung, who is making his first appearance in the last 16 of a Grand Slam.

There were early opportunities on the Djokovic serve for Ramos-Vinolas, but the Spaniard was the first to be broken, in the fourth game, as the Serb took the first set.

At points it looked like a regulation match for Djokovic but concerns for his chances were raised when he called for the trainer with the score 2-1 in the second set.

He continued to hobble and stretch his left leg following the treatment but fought off four break points for Vinolas-Ramos at 4-2 in the second set to maintain his advantage, after which the match always looked to be going in Djokovic’s favour.

“These kind of circumstances in which I’m in at the moment are quite different,” added Djokovic.

“I’ve never faced a situation where I didn’t compete six months.

“That’s why I’m kind of forced to be very cautious of what happens day-to-day, be dedicated to my body and training.”

Gasquet fails to halt losing streak

Federer, 36, comfortably extended his record over Gasquet to 17-2, with the Frenchman only ever having beaten the 19-time Grand Slam champion on clay.

Gasquet, 31, was behind almost immediately in Saturday’s night session and failed to muster a single break point until late in the third set, when he clawed his way back to 4-4.

Federer slammed the door shut on any sustained comeback, however, clinching victory with a brilliant return game after one hour and 59 minutes with two backhand winners.

“I was able to maybe stay a little more on the offensive than he was,” said the Swiss.

“The second set was tight, the match was close and the end could have gone to a tie-break.”

The defending champion will face Hungarian world number 80 Marton Fucsovics in the last 16.

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Fourth seed Alexander Zverev was knocked out of the Australian Open with a five-set defeat by world number 59 Hyeon Chung in the third round.

Zverev, 20, led by two sets to one but crumbled to a 5-7 7-6 (7-3) 2-6 6-3 6-0 loss against his 21-year-old opponent.

The German, tipped as one of the future stars of men’s tennis, won just five points in the decider.

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He will face six-time champion Novak Djokovic next in his first Grand Slam fourth-round match.

“He’s 50-whatever in the world but this was a top-10 level match from the start till the end of the fourth set, and for him until the end,” Zverev said.

“When he plays like that, there are very, very few people who will beat him.”

Zverev, meanwhile, is still yet to reach a Grand Slam quarter-final despite being ranked number four in the world.

“I have some figuring out to do, what happens to me in deciding moments in Grand Slams,” he added. “It happened at Wimbledon, it happened in New York. It happened here. But I’m still young, so I’ve got time.”

The German became distracted in the fourth set, complaining to the umpire that the court’s floodlights should be switched on.

He then received a warning from the umpire at the start of the fifth set when he smashed his racquet after Chung broke serve.

Berdych overpowers Del Potro

Big-hitting Czech Tomas Berdych fired 20 aces and struck 52 winners in a 6-3 6-3 6-2 victory over Argentine 12th seed Juan Martin del Potro.

Berdych, the 19th seed, goes on to face Italian 25th seed Fabio Fognini, who beat France’s Julien Benneteau 3-6 6-2 6-1 4-6 6-3.

“He was just better than me,” said Del Potro. “He hit very hard, served very well and played a smart game. He deserved to win. No excuses.”

Austrian fifth seed Dominic Thiem cruised through in straight sets against Frenchman Adrian Mannarino.

Thiem will play Tennys Sandgren after the American followed up his victory against Stan Wawrinka in round two with a four-set win over Maximilian Marterer of Germany.

World number one Simona Halep survived an epic battle with unseeded American Lauren Davis to reach the Australian Open fourth round.

The Romanian, 26, had to save three match points in the decider before eventually winning 4-6 6-4 15-13 after three hours and 45 minutes.

The final set lasted 142 minutes before Halep finally served out the match at the fourth attempt.

“I never played a third set so long. I’m almost dead,” she said.

“My muscles are gone. I don’t know how my ankle is because I can’t feel it any more.”

The contest equalled the women’s singles Australian Open record for longest match in terms of games played, tying the 1996 quarter-final between Chanda Rubin Arantxa Sanchez Vicario, which Rubin won 6-4 2-6 16-14.

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Halep served for the match at 5-4, 6-5 and 8-7 in the third set but was denied and later recovered from 0-40 on her own serve with the score 11-10 to the impressive world number 76 Davis.

“Honestly, I thought it’s over at that moment, but was good because I relaxed my arm and I served pretty well those three balls,” said Halep.

“It was not easy, but I just kept playing. I just kept believing that it’s not over, even if she’s leading a little bit more.

“I gave everything I had today, and actually, I’m really proud that I could stay there and win it. It was not easy at all. She played great.”

She will play Naomi Osaka in the last 16 after the Japanese player beat Australian 18th seed Ashleigh Barty 6-4 6-2.

‘Incredible warriors’ go through pain barrier

Davis was twice treated for a toenail injury in the latter stages while Halep, who had an ankle problem in the opening rounds, was also limping and holding her upper leg.

Asked if her toenail came off, Davis said: “It’s about to.

“It was very difficult. I had never really had that happen before. I couldn’t really put any pressure on them.”

The 24-year-old added: “That third set was nothing really like I had ever played before. We were both fighting our hearts out.

“Every point was just super long. I got to the point where I was so tired I just told myself to swing and move, and for the most part it was very effective.”

American former Grand Slam winners Chris Evert and Tracy Austin praised both players after the match.

“So impressed with the great effort from Lauren Davis and Simona Halep. Both deserved to win that match,” 18-time Grand Slam singles champion Evert said.

Austin, a two-time US Open winner, said: “Simona Halep and Lauren Davis are incredible warriors! Both ladies should be so proud. Kept digging deeper when it looked like there was nothing left in the tank!”

Pliskova through in straight sets

Elsewhere, Czech sixth seed Karolina Pliskova beat compatriot Lucie Safarova 7-6 (8-6) 7-5 to reach round four.

French eighth seed Caroline Garcia came through in three sets 6-3 5-7 6-2 against Belarus’ Aliaksandra Sasnovich.

She will play American 17th seed and 2017 US Open runner-up Madison Keys who progressed with a 6-3 6-4 win over Romania’s Ana Bogdan.