Giron edged the number five seed from Argentina 7-6 (5), 7-6 (4) in one hour and 41 minutes. Giron lost only five points on his first serve and never faced a break point.

Chinese teen Shang Juncheng also scored an upset with a 7-5, 3-6, 7-6 (4) victory over number seven seed Tomas Martin Etcheverry of Argentina. The 19-year-old qualifier fired 38 winners, including 11 aces. Monday's other winners were Great Britain's Billy Harris and Australia's Max Purcell and Aleksandar Vukic.

Mallorca Championships

Sixth-seeded Frenchman Gael Monfils earned a satisfying 6-3, 7-6 (3) win against Austria's Dominic Thiem in a first-round match in Mallorca, Spain.

Monfils, playing on grass for the first time since Wimbledon in 2021, had been 0-6 head-to-head against Thiem. He turned the tide by striking 13 aces, winning 89.7 percent of his first serves (35 of 39) and never facing a break point.

Number five seed Luciano Darderi of Italy defeated Spain's Pedro Martinez 7-5, 7-5. Italy's Fabio Fognini was a 7-6 (4), 7-6 (5) winner over Dutchman Gijs Brouwer. Australian Rinky Hijikata, Austrian Sebastian Ofner and Kazakhstan's Alexander Shevchenko also moved into the second round.