Top-seeded Victoria Azarenka suffered a blow for the second successive year at the Dubai Open when she pulled with a heel injury, ensuring that Serena Williams will hold on to the world number one ranking this week.
Azarenka, the only unbeaten leading player on the tour this year, beat Williams in three sets in the final of the Qatar Open on Sunday, having played through part of that tournament with painkillers.
Now, however, the bruising continues to cause pain in practice and the Belarussian has decided against risking it any further. Last year she also won the Qatar Open and similarly withdrew from the Dubai Open with a foot injury.
Azarenka would have regained the top spot had she won the title this week. Instead Williams is likely to remain number one at least until the Indian Wells tournament next month.
"I'm very disappointed, but I have to listen to my body," said Azarenka, who suffered a ranking oddity by losing the world number one spot to Williams yesterday despite a rare success against the American the day before.
"The injury happened last week when I played a lot of tennis, so going on to a new tournament is just too much. The heel kept getting worse, and I needed to re-evaluate.
"Sometimes the schedule is just too difficult. Unfortunately you can't know when you plan it in November what will happen in February.
"I didn't want to continue taking painkillers because sometimes it's better to feel the pain. so that you can control the injury. Otherwise it can cause something which is much worse.
"This is just a warning that I have to take care of myself."
Azarenka also admitted that planning a schedule would become "progressively more difficult" as the women's game is becoming more and more physically demanding.
This was something which became clearer, she said, after she had won the Australian Open for the second successive time last month.
"I never realised before just how much it takes out of you," she said. "Physically and mentally it just drains you out - and then you realise."
Williams, who ended the Australian Open with back and ankle injuries and a cold, said in contrast to Azarenka, that she had improved physically a great deal during the Qatar Open.
"I was really, really, really, really sick last week and physically I just wasn't at my best, considering I couldn't train, and I didn't practise," she said.
"I practised only one or two days before playing because I had the ankle problems. But I didn't want to not show up and not play. So at least if I could show up and play my way into shape I would be able to compete and that's what I did.
"I feel so much better this week already. I feel like a completely different athlete, and a completely different person, compared with last week."
Williams is now the overwhelming favourite to win the $2,000,000 Dubai Open for the first time.
However after starting against Marion Bartoli, the world number 11 from France tomorrow (Wednesday), she may go on to a potentially difficult semi-final with the titleholder, Agnieszka Radwanska of Poland.