Sixth seed John Isner sent down an Atlanta Open joint record 36 aces as he overcame countryman Jeffrey John Wolf in three sets on Tuesday.
World number 35 Isner was dominant on his first serve, winning 6-4 6-7 (3-7) 6-4 to claim a spot in the second round where he will face Jack Sock who beat Ricardas Berankis in three.
Isner's 36 aces equaled the previous Atlanta Open record set by Sam Querrey on Monday in his three-set win over Peter Gojowczyk.
American fifth seed Taylor Fritz also progressed on Tuesday with a 6-3 6-4 victory over Russian Evgeny Donskoy.
French seventh seed Benoit Paire got past Japan's Yasutaka Uchiyama 7-5 6-7 (2-7) 6-4, while enigmatic Australian Nick Kyrgios beat South African Kevin Anderson 7-6 (7-4) 6-3.
Teenage American talent Brandon Nakashima knocked out Trent Bryde, while Australian Chris O'Connell beat Denis Kudla and Finland's Emil Ruusuvuori got past Mackenzie McDonald 7-6 (7-3) 7-5.
Nakashima, who got a special exemption entry into the Atlanta Open, next takes on top seed Milos Raonic.
 @JohnIsner hit a personal tournament-best 36 aces in his 6-4, 6-7(3), 6-4 win over Wolf @ATLOpenTennis. It was the 6th time Isner hit 30+ aces in Atlanta. The 36 aces also ties the #AtlantaOpen record, set by @SamQuerrey on Monday.— ATP Media Info (@ATPMediaInfo) July 28, 2021