Americans struggled on the opening day of men's main draw at the ASB Classic tennis tournament in Auckland with Chris Eubanks the first seed to fall.
Eubanks, the only seeded player in action on Monday, was tested by Dutchman Botic van de Zandschulp in their first meeting on the tour and couldn't match the 28-year-old world number 59.
The fifth seed in his second appearance in Auckland was coming off a breakout 2023 season that saw him start the year as ranked 123rd and reach a career-high of 29th in July.
Van de Zandschulp was on debut at the Auckland tournament and his 7-6 6-2 win over Eubanks was his first against a top 50 player on an outdoor hard court since he defeated Casper Rudd at last year's ATP Masters 1000 Miami for the biggest win of his career.
Germany's Daniel Altmaier was the first player to win through to the next round with a straight sets victory over American world number 60 Marcos Giron in the first game on centre court.
Altmaier won a first set tie-break and then comfortably took the second set in the ATP 250 match.
Former junior tennis world number one Luca Van Assche caused an upset when the French teenager beat American J.J Wolf, who is ranked 30 places higher than him, in straight sets to move on to the next round against New Zealand-raised Great Britain representative Cameron Norrie.
Van Assche had to come through qualifying to get into the main draw and said that was an advantage against Wolf who beat him the last time they met six months ago.
The 19-year-old is one of six players from France entered into the tournament and he won't be joined by 37-year-old Gael Monfils in the next round.
Monfils opened the night session on centre court against Hungary's Fabian Marozsan in the third match of the day that needed to go to three sets to find a winner.
Battling back from a set down, Monfils won a tense second set tie-break to keep the match going much to the delight of the French fans who had started to chant his name.
As Monfils pulled off shots from barely believable angles, he even seemed to impress himself bowing to the crowd after one particularly tricky shot.
Marozsan kept in the fight and didn't let Monfils play all the crowd-pleasing shots, playing a few of his own as the two players battled right until the end with a third set tie-breaker.
A 6-4 7-6 7-6 win for Marozsan got a standing ovation as the Auckland crowd appreciated what they had seen from two strong players.
The tournament's top seed American world number 17 Ben Shelton, second seed Norrie, third seed Francisco Cerundolo from Argentina and fourth seeded Canadian Felix Auger-Aliassime all had a bye in the first round had will take to the court for the first time on Wednesday.
On Tuesday wild card Canadian Denis Shapovalov will play seventh seed Sebastian Ofner from Austria. Two-time ASB Classic champion Roberto Bautista-Agut will face fellow Spaniard Roberto Carballes Baena and defending champion and wild card Richard Gasquet will be in an all French battle in his first game of the tournament against sixth seed Arthur Fils.
New Zealand's only player in the singles draw, wild card Kiranpal Pannu, has been drawn against eighth seeded Australian Max Purcell on Tuesday.