Taylor Fritz was forced to come from behind to claim a three-set victory over John Isner in the opening round of the Mexican Open in Acapulco on Monday.
Fritz was among the seeds to progress, alongside Casper Ruud, Holger Rune, Francis Tiafoe and Tommy Paul.
The third seed lost the opening set in 29 minutes but rallied back to win 3-6 6-3 6-4 in one hour and 49 minutes over the big-serving world number 38 Isner.
Fritz claimed his first break of the match in the 17th game before levelling things up at one set each, before breaking Isner at 4-4 in the third and serving out for victory.
The win means Fritz will take on Canada's Denis Shapovalov in the second round after he beat Miomir Kecmanovic in three sets, with the American looking to go one better after being runner-up in Acapulco in 2020.
Second seed Ruud found himself in an almighty battle with Argentina's Guido Andreozzi and eventually prevailed 6-4 4-6 7-6 (7-2).
World number four Ruud, ranked 338 places above his opponent, was broken in the first game of each set but dug deep to get the job done in a little under three hours.
Fourth seed Rune got past 2023 Australian Open quarter-finalist Ben Shelton 6-7 (7-9) 6-4 6-2.
Sixth seed Tiafoe overcame Japan's Yoshihito Nishioka 7-6 (8-6) 6-4 while 2023 Australian Open semi-finalist Paul beat Emilio Gomez 6-1 7-6 (7-4).
Defending champion Pedro Martinez was bundled out of the Chile Open in the first round after losing 6-2 6-0 to German qualifier Yannick Hanfmann.
Jaume Munar progressed to set up a second-round clash with top seed Lorenzo Musetti after winning 6-0 6-7 (4-7) 7-6 (7-5) against Alejandro Tabilo.