World number one Lindsay Davenport reached the last 16 of the US Open for the 11th time in her career with victory over Anabel Medina Garrigues.
The American was made to struggle more than the scoreline suggests in a 6-3 6-2 win over the Spaniard.
The former champion, who finished with 24 errors, dropped serve in the opening game and faced break points at 3-3.
But once she came through that game, she grew in confidence and sealed a meeting with France's Nathalie Dechy.
Dechy earlier beat countrywoman Tatiana Golovin 7-5 2-6 6-2.