Top-ranked Victoria Azarenka stayed on course to retain her Qatar Open title after dispatching Sara Errani 6-2, 6-2 Friday to reach the semifinals.
Maria Sharapova advanced by defeating 2011 U.S. Open champion Sam Stosur 6-2, 6-4.
Azarenka won all 14 net points in the match to make it 12 straight victories this year, including winning her second straight Australian Open title. Serena Williams is challenging the Belarusian for the No. 1 ranking, but had little trouble against the sixth-ranked Italian.
"The score never tells the whole story, really. We had a lot of really long rallies. I was expecting that. She's a very good fighter," Azarenka said. "I really felt like I took big advantage of the important moments, stayed aggressive, and really dictated my game."
The third-ranked Sharapova, looking for her third title in Qatar, will play either Williams or Petra Kvitova. If Williams reaches the semifinal, the 31-year-old American will be the oldest woman to reach No. 1. Chris Evert held the top ranking in 1985 just shy of her 31st birthday.
If Williams loses to Kvitova, Azarenka would retain top spot by reaching the final. Sharapova would return to No. 1 if the other two falter and she wins the tournament.
Sharapova broke twice to lead 4-1 in the first set. She took a 3-0 lead in the second before Stosur staged a brief comeback, but she missed a chance to tie it 4-4. The Russian closed it out when her backhand clipped the net and dropped over.
"I really started playing well when I had to and being aggressive at the right times," Sharapova said. "On the important points when I had to, I came up with really great first serves. That helped me win."
Asked about possibility becoming No. 1 again, Sharapova said it is out of her control.
"Maybe it's not as important as winning the match point of a Grand Slam. Whereas, you wake up on a Monday morning and the ranking system changed and you're No. 1 in the world," she said.