MELBOURNE, Jan 19: Roger Federer was in no mood to let a trend develop after the first real upsets of the week at the Australian Open tennis on Saturday and slapped down local upstart Bernard Tomic with authority to reach the fourth round.

Juan Martin del Potro stunned Federer to win the US Open in 2009 but the Argentine sixth seed was on the receiving end of the shock on Saturday when an inspired Jeremy Chardy led a four-strong French charge into the last 16.

Serena Williams and Andy Murray never looked like losing sometimes challenging contests earlier in the day but defending champion and world No 1 Victoria Azarenka had a closer call and was forced to dig deep for her victory.

All eyes were on the evening match in Rod Laver Arena, however, where Tomic had been talking up his chances of translating his good early-season form into a victory over a player rated by many as the best to ever pick up a racket.

Tomic gave his best and came within two points of winning a thrilling second-set tiebreak but the 17-time Grand Slam champion simply upped the gears, pulled out a couple of extraordinary winners, and raced away to a 6-4, 7-6, 6-1 victory.

Del Potro battled back from two sets down to level his third-round contest but the mercurial Chardy grabbed a break in the decider and held his nerve to serve out for a 6-3, 6-3, 6-7, 3-6, 6-3 win.

After five days without any upsets of note at the year's first Grand Slam, two came along within minutes.

As Chardy was packing up his rackets on Hisense Arena, Italian Andreas Seppi was securing his place as the Frenchman's next opponent by wrapping up a 6-7, 6-3, 2-6, 6-4, 6-2 win over Croatian 12th seed Marin Cilic, a semi-finalist in 2010.

Azarenka had to come back from a break down in the deciding set to avoid the same fate against injury-hampered American Jamie Hampton and her relief at her 6-4, 4-6, 6-2 win was clear.

“She took a medical timeout but she rips winners all over the place,” said Azarenka. “I was like: 'Can I have a back problem? I'm feeling great but I'm missing every shot'.”

Williams, seeking a sixth title at Melbourne Park, also wobbled a bit at 3-0 down in the second set against world No 72 Ayumi Morita after losing her serve for the first time in the tournament.

The third seed showed no discomfort from the ankle strain she sustained in the opening round, however, and stormed back to win the next six games and dismiss the Japanese 6-1, 6-3.

US Open champion Murray berated himself for playing ‘nonsense’ tennis at times but eventually broke down his Lithuanian practice partner Ricardas Berankis 6-3, 6-4, 7-5 after a tricky 132 minutes in the Melbourne sun.

Murray was able to put his feet up and watch his next opponent Gilles Simon beat compatriot Gael Monfils 6-4, 6-4, 4-6, 1-6, 8-6 in a four-hour, 43-minute marathon that ensured four Frenchman would be in the fourth round for the first time since 1998.

Ninth seed Richard Gasquet's progress was by no means smooth and he was a set and a break down before he charged back to beat Croatian Ivan Dodig 4-6, 6-3, 7-6, 6-0.

His seventh-seeded compatriot Jo-Wilfried Tsonga had an easier day, hammering Blaz Kavcic 6-2, 6-1, 6-4.

Japan has also had a good tournament but Kimiko Date-Krumm's fairytale run came to an end with a 6-2, 7-6 defeat to Serbian Bojana Jovanovski, who was born two years after her 42-year-old opponent made her debut at Melbourne Park.

Results (prefix number denotes seeding): Men’s singles: Third round: 14-Gilles Simon (France) bt Gael Monfils (France) 6-4, 6-4, 4-6, 1-6, 8-6; 2-Roger Federer (Switzerland) bt Bernard Tomic (Australia) 6-4, 7-6 (7-5), 6-1; 13-Milos Raonic (Canada) bt 17-Philipp Kohlschreiber (Germany) 7-6 (7-4), 6-3, 6-4; 3-Andy Murray (Britain) bt Ricardas Berankis (Lithuania) 6-3, 6-4, 7-5; 21-Andreas Seppi (Italy) bt 12-Marin Cilic (Croatia) 6-7 (2-7), 6-3, 2-6, 6-4, 6-2; Jeremy Chardy (France) bt 6-Juan Martin Del Potro (Argentina) 6-3, 6-3, 6-7 (3-7), 3-6, 6-3; 7-Jo-Wilfried Tsonga (France) bt Blaz Kavcic (Slovenia) 6-2, 6-1, 6-4; 9-Richard Gasquet (France) bt Ivan Dodig (Croatia) 4-6, 6-3, 7-6 (7-2), 6-0.

Women’s singles: Third round: Bojana Jovanovski (Serbia) bt Kimiko Date-Krumm (Japan) 6-2, 7-6 (7-3); 29-Sloane Stephens (US) bt Laura Robson (Britain) 7-5, 6-3; 10-Caroline Wozniacki (Denmark) bt Lesia Tsurenko (Ukraine) 6-4, 6-3; Elena Vesnina (Russia) bt 16-Roberta Vinci (Italy) 4-6, 7-6 (7-4), 6-4; 3-Serena Williams (US) bt Ayumi Morita (Japan) 6-1, 6-3; Svetlana Kuznetsova (Russia) bt Carla Suarez Navarro (Spain) 6-2, 4-6, 6-3; 1-Victoria Azarenka (Belarus) bt Jamie Hampton (U.S.) 6-4, 4-6, 6-2; 14-Maria Kirilenko (Russia) bt 20-Yanina Wickmayer (Belgium) 7-6 (7-4), 6-3.—Reuters