The Williams sisters could be headed for a final matchup at the Sony Ericsson Championships after Venus advanced to the knockout rounds along with Jelena Jankovic and Caroline Wozniacki.
Venus, the defending champion, lost her first two group matches but advanced on a countback of sets thanks to Svetlana Kuznetsova’s 6-3, 6-2 win over Elena Dementieva. Venus joined unbeaten sister Serena Williams in the semifinals from the Maroon Group.
Jankovic advanced by routing a tired Wozniacki 6-2, 6-2, but the 19-year-old Dane also went through from the injury-plagued White Group when Victoria Azarenka had to retire against alternate Agnieszka Radwanska of Poland when trailing 4-6, 7-5, 4-1 in the most dramatic match of the day.
Azarenka would have advanced with a win, and served for the match twice in the second set. She needed a medical time-out early in the third to treat her left thigh and lower back.
She continued playing but hobbled around in pain, needing another time-out to treat leg cramps before the final game. She came back out, but finally called it quits while down 40-15.
Serena Williams will play Wozniacki in one semifinal today, and Venus Williams will face Jankovic at the same stage for the second straight year.
Both Williams sisters had the day off after playing on the first three days. The Americans are also playing in the four-team doubles tournament, which starts with the semifinals on Saturday.