MELBOURNE—Defending champion Novak Djokovic wrecked Nicolas Mahut’s birthday on Saturday, losing just two games as he powered through to the last 16 of the Australian Open to join Jo-Wilfried Tsonga.

The Serbian top seed blitzed hapless Mahut 6-0, 6-1, 6-1 in just 74 minutes, reaching the fourth round without dropping a single set so far.

French sixth seed Tsonga, who lost to Djokovic in the 2008 Melbourne final, was also in a hurry, demolishing Portugal’s Frederico Gil, ranked 107th, 6-2, 6-2, 6-2.

Djokovic, who mastered Andy Murray in last year’s final, reached the round of 16 in Melbourne for the sixth straight year, hardly breaking sweat and looking in ominous form.

The world number one will take on either power-serving Canadian Milos Raonic or two-times grand slam champion Lleyton Hewitt in Monday’s fourth round.

Mahut, who shares the record for the longest-ever tennis match of 11 hours and five minutes with John Isner at Wimbledon two years ago, was struggling with a left knee injury on his 30th birthday.

“Credit to Nicolas. Obviously, he had some strapping around his knee and I felt sorry for him,” Djokovic said.

“Evidently he was not moving well, he was not able to perform his best, but he didn’t want to retire and he wanted to stay all the way so I wish him happy birthday.”

Djokovic, who broke Mahut’s serve eight times and made only eight unforced errors in the 20 games, is bidding to become the fifth man to win three consecutive grand slams after winning Wimbledon and the US Open last year.

Djokovic leads Hewitt 4-1 and has yet to play Raonic in an official match.

Tsonga said not having a coach had done him no harm at all after seeing off Gil and is set to play either compatriot Julien Benneteau or Japan’s 24th seed Kei Nishikori next.

Tsonga, the top-ranked French man, parted company with long-time coach Eric Winogradsky last April and has since been on his own.

In that time he has reached the semi-finals at Wimbledon and the US Open quarter-finals.

After putting Gil to the sword on Saturday, the 26-year-old Frenchman said he saw no pressing need to recruit a replacement mentor.

“I mean, it’s not the first one (tournament without a coach), so I feel good. I’m OK,” he said. “You can also improve your game by yourself. I’ve improved a lot.

“I’m here because maybe I had a coach, but now I feel like I have to follow my opinion maybe a bit more.”