Nice - Second-seeded John Isner has hit 16 aces to reach the quarter-finals of the Open de Nice in a tight all-American contest with Steve Johnson on Tuesday.
Isner was made to play for nearly two hours by the 55th-ranked Johnson before sealing a 7-6 (3), 4-6, 6-3 victory.
"It was a pretty good match, I thought we both played pretty well," Isner said.
"In the third set, I was fortunate to get that break and held on from there."
No. 8 seed Juan Monaco also made it to the quarter-finals after he broke Sam Querrey five times in a 6-3, 6-1 win.
Sixth-seeded Nick Kyrgios used his strong serve to reach the second round with a 7-6 (5), 6-2 win over Mikhail Kukushkin.
The 20-year-old Kyrgios, who is among the outsiders at the French Open after making the final at the Estoril Open and beating Roger Federer in Madrid, lost only two points on his serve in the second set and converted three of his five break chances.
The 30th-ranked Australian will next face Dominic Thiem.
French qualifier Gianni Mina advanced when fifth-seeded Bernard Tomic retired with a virus after losing the opening set 6-2, and James Duckworth rallied past lucky loser Frances Tiafoe 6-7 (5), 7-5, 6-2 to set up a second-round match with top-seeded Gilles Simon.
Tiafoe, a 17-year-old American, has earned a wild card for the French Open, which starts on Sunday.
Seventh-seeded Jack Sock lost 5-7, 7-5, 6-1 to Dusan Lajovic in the first round and wild card Lucas Pouille breezed past Tim Smyczek 6-3, 6-0.