Sixth seed Fabio Fognini was sent packing in the first round of the Argentina Open on Tuesday after he was beaten 7-6 (4), 4-6, 4-6 by Federico Delbonis.
Fognini found himself in an advantageous position after winning a gruelling first set, but he began to struggle in the second, leaving the door open for Delbonis to make his comeback.
Delbonis completed the upset by breaking Fognini in the 10th game of the third set to seal the victory.
Delbonis will face Nicolas Almagro in the second round after the Spaniard beat his compatriot Albert Montanes 6-3, 6-3 on Monday.
Meanwhile, fifth seed Dominic Thiem fought his way past Pablo Carreno Busta 6-0, 3-6, 6-3 and eighth seed Pablo Cuevas downed Albert Ramos-Vinolas 7-5, 6-2.
Juan Monaco, Paolo Lorenzi, Dusan Lajovic, Gastao Elias and Renzo Olivo also progressed to the second round.