Top seed Agnieszka Radwanska pulled out of the BMW Malaysian Open on Friday due to injury after a string of rain delays caused a schedule pile-up that forced her to face two opponents the day before.
"I'm so sorry I can't continue. Had a great time in Malaysia and I hope to be back in future," the Polish world number five told the centre court crowd in conceding her quarter-final match-up with Taiwanese qualifier Su-Wei Hsieh.
Radwanska did not address the reason for her withdrawal, but Women's Tennis Association tour supervisor Pam Whytcross said the Pole had an elbow injury.
"We were called into the training room at 2 p.m. and were informed that she had a right elbow injury," Whytcross said.
Radwanska arrived in Malaysia on the back of a win in Dubai last Saturday, a result which saw her rise to a career high in the WTA rankings.
But her first-round match with Akgul Amanmuradova -- originally scheduled for Tuesday -- was pushed back a day due to heavy rain at the Bukit Kiara Equestrian and Country Resort in the Malaysian capital Kuala Lumpur.
The match was again halted by heavy showers on Wednesday with Radwanska leading 6-2, 3-3.
It was only completed early Thursday afternoon and giving Radwanska two hours before returning to court to defeat Karolina Pliskova 6-4, 6-4.
"It is disappointing but we wish her the best. It is still early in the season and the players have to manage their injuries carefully," Whytcross said.
Radwanska had been wearing a thigh strap in the tournament while also complaining about a sore shoulder after beating Pliskiova.
Meanwhile, fifth seed Petra Martic came back from an opening-set loss on Friday to upset third seed Peng Shuai of China, 4-6, 7-6 (7/3), 6-4.