Ashleigh Barty moved to within two matches of becoming world number one after beating Venus Williams 6-4 6-3 to reach the semi-finals of the Nature Valley Classic in Birmingham.
The French Open champion will overtake Naomi Osaka at the top of the rankings if she wins the title on Sunday.
Barty, 23, won five games in a row to take the first set and then broke Williams' serve twice in the second.
The Australian will face Barbora Strycova in the semi-finals.
"You start to think ahead, it's natural, it happens," Barty said of the potential number one ranking. "It's important for me to come out and focus tomorrow [Saturday]. Whatever happens, happens."
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Strycova got the better of an all-Czech battle to beat Kristyna Pliskova 6-2 6-4.
In the other semi-final, Germany's Julia Gorges takes on Croatia's Petra Martic, who survived five match points to overcome former French Open champion Jelena Ostapenko 6-7 (4-7) 7-5 6-1.
Martic trailed 5-2 in the second set having lost the first on a tie-break, but rallied to win the next five games before taking the third 6-1.
"I still can't believe that I won this match," said Martic.
Gorges, a Wimbledon semi-finalist in 2018, beat Yulia Putintseva 6-3 6-2.
At the Mallorca Open, reigning Wimbledon champion Angelique Kerber beat French sixth seed Caroline Garcia 6-3 7-6 (7-5) to reach the semi-finals, where she will face Belinda Bencic.
American 20-year-old Sofia Kenin will play Latvian second seed Anastasija Sevastova in the other semi-final. Kenin beat Elise Mertens 1-6 6-1 6-3, while Sevastova defeated Wang Yafan 6-2 6-1.