LOS ANGELES (AFP) - Former world No. 1 Venus Williams crashed out of the WTA Chicago Women's Open on Monday (Aug 23), losing in straight sets to Taiwan's Hsieh Su-wei, 6-2, 6-3.

The seven-time Grand Slam winner Williams, who is the oldest player in the draw at 41, spent just 67 minutes on the court in a one-sided opening round match at the Washington Park tennis facility on Chicago's South Side.

Williams is now just 3-9 on the season and has seen her ranking drop to 147 in the world. Of those nine losses this season, two have been against the 125th-ranked Anna Karolina Schmiedlova.

It was one of the biggest wins of the 81st-ranked Hsieh's career as she improved to 11-12 on the season. She made it to the quarter-finals of the Australian Open earlier this year, losing to Naomi Osaka 6-2, 6-2.

In 2018, she upset then world No. 1 Simona Halep in the third round of Wimbledon.

The 35-year-old Hsieh kept Williams on her back foot with a strong service game and precision cross court and down the line forehands.

She won 71 per cent of her first serve points and had just one double fault, while Williams double faulted five times. Williams, who has 49 career WTA titles, had her serve broken four times and won just 35 per cent of her second serve points.

In other matches on Monday, top seed and Tokyo Olympic bronze medallist Elina Svitolina was ahead 2-0 in the deciding third set when France's Clara Burel retired from their match.

Kristina Mladenovic defeated Zarina Diyas 6-2, 7-6 (7-3), and Czech Tereza Martincova surprised third seed Sorana Cirstea 3-6, 6-3, 6-2.