Venus Williams continued her comeback from injury by reaching the Memphis International quarter-finals with a 6-4, 6-4 win over 16-year-old Dane Caroline Wozniacki on Tuesday.
In her first event in more than four months because of wrist and knee injuries, former world number one Williams staved off a late rally from her opponent to reach the last eight.
After struggling past Japan's Akiko Morigami in the first round, Williams showed a few flashes of her old self as she battled back from a poor start.
Wozniacki, who reached the quarter-finals in Memphis last year as a 15-year-old, played smartly and consistently to lead 4-2.
But the seventh-seeded American won eight successive games to win the first set and take a 4-0 lead in the second.
Wozniacki fought back to 4-4 but Williams held serve and clinched victory on her fourth match point to set up a quarter-final clash with fellow American Laura Granville or Slovakian Jarmila Gajdosova.
"It was definitely a better match for me [than the first-round match]," Williams told reporters.
"I had a lot of good streaks in the match. She did a good job of coming back but when it was tight I played some good points, so that's good to know.
"I am being aggressive and going for my shots."
American Meilen Tu joined Williams in the quarter-finals with a surprise 6-3, 6-1 victory over her compatriot Jill Craybas, the eighth seed.
In first-round action, top seed Shahar Peer of Israel battled past Finland's Emma Laine 6-4, 6-3 to set up a clash with Milagros Sequera of Venezuela, who beat Russian qualifier Alina Jidkova 6-4, 1-6, 7-5.
Fourth-seeded Australian Samantha Stosur moved into the second round with a 6-2, 7-5 win over Canadian Aleksandra Wozniak and there were also victories for Camille Pin of France, and Swede Sofia Arvidsson.