Top seed Jelena Jankovic went out of the Kremlin Cup at the first hurdle in a 6-1 6-2 thrashing by little-known Kazakh teenager Zarina Diyas on Thursday.
Serbia's former world number one, who had a bye in the first round, looked out of sorts from the start, committing numerous errors and winning only 43 percent of her first serves. She was beaten in less than an hour by the 268th-ranked Diyas.
"I'm not feeling well. I have been sick since I came from China," said Jankovic, who also suffered a second-round defeat at the China Open earlier this month.
"I got an infection and have been on antibiotics for a week or so and unfortunately I wasn't ready to play at my level.
"I was suffering a lot but I didn't want to retire. It was tough for me to focus on my tennis. I had a hard time breathing and I was getting tired quickly and didn't have much energy."
Jankovic said she would try to recover for next month's season-ending WTA championships in Doha.
"I just hope that I can recover and feel better for Doha," the world number seven said.
"I'll see the doctor now and see what I can do. It's tough, it's the end of the year, my body is exhausted. It's been a long season with lots of travelling. I have one more tournament left and hope I can at least be healthy so I can go there and play."
{{/usCountry}}"I'll see the doctor now and see what I can do. It's tough, it's the end of the year, my body is exhausted. It's been a long season with lots of travelling. I have one more tournament left and hope I can at least be healthy so I can go there and play."
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