MELBOURNE, AUSTRALIA - JANUARY 17: Jie Zheng of China plays a forehand during her first round match against Madison Keys of the United States during day two of the 2012 Australian Open at Melbourne Park on January 17, 2012 in Melbourne, Australia. (Photo by Ryan Pierse/Getty Images)

Auckland – Defending champion Zheng Jie crashed out in the first round of the ASB Classic women's tennis tournament Monday, falling to rising American star Jamie Hampton 7-5, 6-1.

Two-times Grand Slam winner Svetlana Kuznetsova was also sent packing on the opening day, beaten in a three-set marathon by Kiki Bertens of the Netherlands.

Zheng, seeded fourth in the tournament that serves as a warm-up to next month's Australian Open, raced to an early 3-0 lead in the opening set before Hampton fought back to level at 5-5.

The German-born American, who has soared up the rankings from 137 to 70 over the past year, then broke Zheng in a love game before taking out the set with an ace in the following game.

The second set was all Hampton, as she used her strong cross-court forehand to dominate the more experienced Chinese in one hour 20 minutes.

In blustery conditions, the 21-year-old Bertens fought back from a set down to beat former world number two Kuznetsova 6-7 (5/7), 6-2, 7-5.

Bertens, who has risen in the rankings from 184 to 63 during 2012, grew in confidence despite serving 10 double faults in the strong wind.

After losing the opening set tie-break in the 2hr 33min marathon, she held her concentration against the 28-year-old Russian veteran, who is making a comeback after a first-round knee injury at Wimbledon ended her 2012 season.

American Christina McHale was the second ranked player dumped out on the opening day, with the seventh seed losing in straight sets to France's Pauline Parmentier 6-4, 6-1.

Tournament top seed Agnieszka Radwanska has her opening match on Tuesday against 2011 winner Greta Arn, who had to rely on the luck of the draw to make the field this year.

Arn lost her final-round match in the qualifying tournament to Thai player Nudnida Laungnam. But her name was later drawn at random from among four players to replace Kristina Mladenovic, who was a late withdrawal from the Classic. – Sapa-AFP