Buenos Aires - Federico Delbonis of Argentina upset sixth-seeded Fabio Fognini of Italy 6-7 (4), 6-4, 6-4 in the first round of the Argentina Open on Tuesday.
But eighth-seeded Pablo Cuevas of Uruguay had better luck, beating Albert Ramos-Vinolas of Spain 7-5, 6-2 to reach the second round.
In other matches, Renzo Olivo of Argentina defeated countryman Facundo Bagnis 7-6 (9), 7-5, and Portugal's Gastao Elias beat Daniel Munoz de La Nava of Spain 4-6, 6-4, 6-1.
The top four seeded players all have byes into the second round: No 1 Rafael Nadal, No 2 David Ferrer, No 3 Jo-Wilfried Tsonga and No 4 John Isner. Nadal is the defending champion.
The Buenos Aires tournament is the second of four consecutive events on clay around Latin America.