Serena Williams was pushed hard for the third successive match before reaching the fourth round of the US Open.
Serena had to be at her battling best once again
The eighth seed took nearly two hours to despatch Russian Vera Zvonareva 6-4 7-6 and book a meeting with Wimbledon finalist Marion Bartoli.
"I was upset after the match. I didn't feel that I played the greatest at all," said Williams.
"I actually felt like I didn't play well at all. But that's said and done. I'm moving on."
Zvonareva was playing her first event since April but was more than a match for Williams from the baseline.
The Russian lost a tight first set and was a break up in the second before former champion Williams prevailed.
Venus Williams had a much easier time of it as she crushed Alona Bondarenko 6-1 6-2 to book a fourth-round meeting with Ana Ivanovic.
The Wimbledon champion, seeded 12th, managed to get only 51% of her first serves in but she also despatched 30 winners in a one-sided win.
"I just want to take that experience from Wimbledon and bring it here," she said. "I've done it here before and I want to do it again."
Fifth seed Ivanovic cruised past Russian Vera Dushevina 6-1 6-3.
Ivanovic's fellow Serb Jelena Jankovic survived a third-round scare, dropping the first set before rallying back for a 4-6 6-2 6-3 victory over French teenager Alize Cornet.
Third seed Jankovic said she underestimated the 17-year-old Cornet and was fortunate to advance.
"I was so careless. I underestimated my opponent because I thought she was a junior," said Jankovic, 22.
"I thought I will have an easy job. That was a big mistake for me."
Top seed Justine Henin raced into the fourth round with a comprehensive 6-0 6-2 victory over Ekaterina Makarova of Russia.
The world number one swept through the first set in just 18 minutes and then went 3-0 up in the second set.
Left-hander Makarova, playing in her debut Grand Slam, finally held serve but there was no way back for the 19-year-old as Henin romped through.
Henin, 25, now plays 15th seed Dinara Safina of Russia.
The Belgian has beaten Safina in straight sets on each of the three occasions they have met and Henin is currently more than happy with her game.
"I am healthy - almost 100%, apart from my shoulder. I am very happy with the way I played today," she said.
In other results on Tuesday, Sybille Bammer beat 14th seed Elena Dementieva 6-1 6-2 while Wimbledon runner-up Marion Bartoli had to come from a set down to book her fourth-round spot.
The French 10th seed finally saw off Czech left-hander Lucie Safarova, the 20th seed, 4-6 6-2 6-3.