Top-seeded John Isner hit 13 aces on his way to a hard-fought 7-6 (3), 7-6 (5) win against Belgium's Xavier Malisse at the Open de Nice on Wednesday.
The hard-serving American won a match in which neither player conceded a break point, and will play Nikolay Davydenko in the quarterfinals after the Russian topped seventh-seeded Denis Istomin of Uzbekistan 6-4, 1-6, 6-3.
No. 2 Gilles Simon of France and No. 3 Nicolas Almagro of Spain also advanced to the last eight.
Simon downed Bulgaria's Grigor Dimitrov 6-3, 6-3 and will play Brazilian Thomaz Bellucci, who beat Spain's Juan Carlos Ferrero 6-4, 6-3.
Almagro overcame Frenchman Edouard Roger-Vasselin 7-6 (5), 6-4 and will face Steve Darcis of Belgium, who rallied past Italian Filippo Volandri 3-6, 6-2, 6-4.
But fourth-seeded Gael Monfils of France was knocked out by American Brian Baker, who is ranked 216th and is playing in his first tour-level event since the 2005 U.S. Open - and his first ever on clay.
Baker next faces Mikhail Kukushkin of Kazakhstan after he rallied from 4-2 down in the deciding set and saved four match points to overcome No. 5 Bernard Tomic of Australia 3-6, 6-2, 7-5.