Defending champion Novak Djokovic reached the Wimbledon third round for the 16th time on Wednesday as potential semi-final opponent Casper Ruud crashed out.

Top seed Djokovic brushed aside 79th-ranked Thanasi Kokkinakis of Australia 6-1, 6-4, 6-2 and will face Serbian compatriot Miomir Kecmanovic for a last-16 place.

Third seed and French Open runner-up Ruud was knocked out by 112th-ranked Ugo Humbert, 3-6, 6-2, 7-5, 6-4.

"I'm very happy with my performance. I started very well, solid from the back of the court," said Djokovic, who is looking to join Pete Sampras as a seven-time Wimbledon champion.

"I made him work for every point and worked him around the court," added the 20-time major winner.

Kokkinakis had likened Djokovic to a "brick wall" before the match.

"It was one-way traffic. I got chopped today," said the 26-year-old Australian after his Centre Court torment.

In the women's event, second seed Anett Kontaveit lost 6-4, 6-0 to Germany's Julie Niemeier as the Estonian endured another Grand Slam to forget.

Kontaveit has made the quarter-finals of a major just once in 29 attempts.

Ninth seed and 2017 champion Garbine Muguruza also exited in her delayed first-round clash, losing 6-4, 6-0 to Belgium's Greet Minnen.

Amazing support

Lesia Tsurenko came out on top in three sets over Ukrainian compatriot Anhelina Kalinina to make the third round for the second time.

Tsurenko, ranked at 101, proudly wore a ribbon in the colours of Ukraine on her shirt.

"It was a big court. Two Ukrainian players but a lot of people were watching us. We felt amazing support," said Tsurenko after her 3-6, 6-4, 6-3 win.

"Today on the way from hotel to the club, we got a driver," she added. "She has taken two people from Ukraine into her house. 

"I think it's amazing when people help Ukrainians so much."

Later Wednesday, two-time champion Andy Murray puts his 8-0 record against John Isner on the line in their second-round clash.

Former number one Murray, now down at 52 in the world, needed four sets to defeat Australia's James Duckworth on Monday.

At one point, the British star dropped in an underarm serve to carve out a winning point, much to the delight of the Centre Court crowd.

"I don't know why some people find it disrespectful," said Murray.

Despite his losing record against Murray, 37-year-old Isner has never played the Briton on grass.

He is confident he has the weapons at his disposal, having fired 54 aces to knock out qualifier Enzo Couacaud on Monday.

"I'm older than Andy, I'm no spring chicken, but I work hard," said the American, who stands 6 feet 10 inches (2.08 metres) tall.

Isner has now served 13,688 aces in Tour-level matches during his career -- just 40 behind the record of 13,728 held by Ivo Karlovic.

Isner was one of 13 American men to reach the second round, the most since 1995.

Spanish teen sensation and fifth seed Carlos Alcaraz aims for a place in the last 32 for the first time when he meets Tallon Griekspoor of the Netherlands.

Britain's US Open champion Emma Raducanu tackles France's Caroline Garcia, who collected her third grass-court title at Bad Homburg last week.