Jelena Jankovic was relieved she didn't suffer the same fate as Venus Williams as the world No1 battled past Japan's Ai Sugiyama 6-4, 6-4 today, writes Chris Jones.

Seven-time Grand Slam champion Williams yesterday fell victim to the biggest shock of the tournament so far, losing to the unseeded Spaniard Carla Suarez Navarro.

Jankovic said: "There are so many good players in the draw and I saw Venus lose her match and it was a huge win for her opponent.

"No one is afraid of anyone and that makes it a great competition and very unpredictable."

The top seed gained a double break in the first set to lead 4-1 before Sugiyama fought back to 4-3. Her momentum ended there, however, and Jankovic sealed the set when the 26th seed netted a forehand smash.

The match developed into a girtty affair, the set going with serve until the seventh game when Jankovic seized her first opportunity and broke to take a 4-3 lead.

The 33-year-old Sugiyama then took a medical time-out for treatment to her back and left leg, before the Serb went on to wrap up victory in one hour, 41 minutes.

Sugiyama forces her opponents to play extra shots to win the point with her amazing court coverage and, at times, that stretched Jankovic, who also struggled to cope with the conditions.

Jankovic, who now faces France's 16th seed Marion Bartoli, said: "I feel like I am on fire because of the heat on court and I took my tennis shoes off as many times as I could."

Dinara Safina defeated Estonia's Kaia Kanepi 6-2, 6-2 to reach the fourth round for the first time in Melbourne at the head of a strong Russian challenge.

With Russia's Maria Sharapova unable to defend her title, it has fallen to the sister of Marat Safin to assume the role as leading contender from one of the strongest nations in the sport and her No3 seeding is testament to the improvements she made last year, which included making the French Open Final.

The 6ft Safina said: "I have to use my power because there is no other way. I am not a road runner on the court and I cannot be as fast as some other players, but I have some other weapons. If I use my power, then I have to run less. It's time to use it sometimes."

She will now face 15th seed, France's Alize Cornet (right), who beat 19th seed Daniela Hantuchova, of Slovakia, 4-6, 6-4, 6-2.