Nicolas Almagro of Spain and Federico Delbonis of Argentina picked up second-round victories on Thursday and are set to meet in the quarterfinals of the Copa Claro in the Argentine capital.
Second-seeded Almagro defeated Andrey Kuznetsov of Russia 7-6 (5), 6-2. Delbonis won against Albert Montanes of Spain 6-1, 6-4.
Almagro struggled in the first set.
"It was not a very good match for me," he said. "The important thing is being in the quarterfinals again."
Almagro won this tournament two years ago and was the runner-up last year to fellow Spaniard David Ferrer. This is his sixth appearance in the quarterfinals.
"It's always nice coming here," he said. "I feel really good and I feel loved by the people here. Six times in the quarterfinals says a lot, and a title, too."
Ferrer is the top seed again and played late Thursday against David Nalbandian of Argentina. No. 3 Stanislas Wawrinka faced Daniel Gimeno-Traver, also in a late match.