Kuala Lumpur – Second seed and defending champion Hsieh Su Wei of Taiwan overcame fatigue, leg cramps and two opponents Thursday to reach the quarterfinals of the rain-delayed BMW Malaysian Open.

Hsieh, who ranks world number 23 and is hoping to become the first player to successfully defend the title, started her day by beating Kurumi Nara of Japan 6-7 (5-7), 6-3, 6-4 in a match held over from Wednesday.

She was leading 4-3 when the match was halted Wednesday due to rain. She needed another two hours to complete her first round match Thursday and was back on court three and a half hours later to face Zhang Shuai of China.

Hsieh, who needed two medical times against Nara, was energised by her break and romped past Zhang 6-3, 6-3 in 73 minutes.

The 27-year-old will now face wildcard entry Bethanie Mattek-Sands, who stormed into the quarterfinals when she crushed Duan Ying-Ying of China 6-1, 6-4.

The bubbly blonde, who is known as the Lady Gaga of tennis after attending the 2011 pre-Wimbledon party in a dress made of tennis balls created by the popstar's designer Alex Noble, hardly broke a sweat as she brushed aside her opponent.

The colourful American, who also sports several tattoos, was one of five players to secure quarter-final berths so far.

The others who have qualified for the quarter-finals are Japanese fourth seed Ayumi Morita, Karolina Pliskova of the Czech Republic, Australia's Ashleigh Barty, Thailand's Luksika Kumkhum and third seed Anastasia Pavlyuchenko of Russia.

Mattek-Sands, who won the doubles title at the Dubai Duty Free Tennis Championships last weekend with India's Sania Mirza, said:

“I've never won any singles title before, even though I have reached a few finals.

“Maybe that first win will come in Malaysia.”

Once ranked world number 30, Mattek-Sands has slipped to 197th. – Sapa-AFP