World number one Iga Swiatek continued to strive for her third consecutive Qatar Open title, but Japan's Naomi Osaka was defeated in Doha.
Swiatek defeated former world number one Victoria Azarenka of Belarus 6-4, 6-0 in just 74 minutes.
The Polish athlete, who has won 11 consecutive matches in Doha, will face in-form Karolina Pliskova in the semi-finals.
Czech Pliskova won 7-6 (8-6), 7-6 (7-5), ending Osaka's best record in nearly two years.
Four-time major champion Osaka returned to tennis last month after giving birth to daughter Shai in July.
The quarterfinal match against Pliskova was her farthest in the tournament since losing to Swiatek in the Miami Open final in April 2022.
Pliskova, who won her first WTA title in four years at the Transylvania Open on Sunday, was broken by Osaka in her first service game but quickly fought back to take the lead in the first set tiebreak.
Osaka saved a match point at 5-4 and two more at 6-5 to force the second set into a tiebreak, but Pliskova made her fourth call after 1 hour and 43 minutes. Decided to succeed.
On the other side of the women's draw in Doha, 2022 Wimbledon champion Elena Rybakina fought back from a 4-1 deficit in the first set to defeat Canada's Leila Fernandez 6-4, 6-2. , ensuring a place in the top four.
The third seed from Kazakhstan will face Russia's Anastasia Pavliuchenkova, who defeated Danielle Collins 7-5, 6-4.
