Jessica Pegula has beaten world number one Aryna Sabalenka in straight sets to move into the semi-finals of the WTA Finals in Cancun, Mexico
Pegula, 29, clinched victory on her seventh match point, sealing a victory over the Belarusian, who made 33 unforced errors.
Elena Rybakina defeated Maria Sakkari.
She will now play Sabalenka on Thursday evening to determine the second qualifier from the group.
American Pegula, who had defeated Rybakina on Sunday, has now won her past five matches against top-10 players and said she is feeling “more comfortable” against the elite players this year.