体坛英语新闻：Federer, Serena reaches fourth round, underdog Charday stuns Del Potro

MELBOURNE, Jan. 19 (Xinhua) -- Former US Open champion Juan Martin Del Potro was stunned 3-6, 3-6, 7-6, 6-3, 3-6 by Frenchman Jeremy Chardy in the third round of the Australian Open here on Saturday, while tournament-favourite Serena Williams and Roger Federer reach the fourth round.

Del Potro, the sixth-seeded Argentine became the highest seed dumped out of the tournament although he only conceded 13 games to his first two opponents, the lowest in the men's draw.

Chardy tallied 78 winners to only 36 for Del Potro. Del Potro struggled to hold his serve, offering Chardy a surprising 17 break points, of which the Frenchman took advantage of five.

Del Potro was barely a factor in the first two sets, unable to find a comfort level on the court. He was clearly frustrated, and smashed a racket early in the encounter.

However, once Del Potro secured the third set, winning the tiebreaker with a scorching forehand crosscourt winner, he seemed ready to turn the match in his favour. In the fourth set, Del Potro took the advantage by breaking Chardy's serve in the eighth game and successfully served for the set at 5-3.

Del Potro eventually lost serve on a second break point of the eighth game on an unforced forehand error, putting Chardy in position to serve out the match. The Frenchman then closed out the contest with an ace.

Serena Williams showed no discomfort from the right ankle injury she sustained in the first round and stayed on track for a third consecutive Grand Slam title by thrashing Japanese Ayumi Morita 6-1, 6-3.

The 31-year-old American, seeking a sixth crown at Melbourne Park, was 0-3 down in the second set before she won six games in a row to end Morita's hope at the Australian Open. She suffered her first service break in the tournament with a double-fault in the second game of the second set.

17-time Grand Slam winner Federer crushed young Australian Bernard Tomic 6-4, 7-6, 6-1 after marching to a clinical 118-minute victory. Federer broke the 20-year-old Tomic's in the first game of the match, ending a run of 76 consecutive service games held by Tomic.

Federer also beat Tomic in the fourth round of last year's tournament.

US Open champion Andy Murray extended his Grand Slam winning streak to 10 matches after beating practice partner Ricardas Berankis 6-3, 6-4, 7-5. But the world No.3 appeared agitated at various stages, hitting his racquet on the court and yelling at his courtside box when he was trailed by a break of serve in the second set.

Women's top seed Victoria Azarenka survived a scare from injured Jamie Hampton. The defending champion came back from a break down in the deciding set to beat Hampton 6-4, 4-6 and 6-2.