Top-seeded David Ferrer defeated fellow Spaniard Albert Ramos 6-1 6-2 on Friday to reach the semi-finals of the ATP tournament in the Argentine capital.
Ferrer, the two-time defending champion in Buenos Aires, is hoping to win his 21st ATP tournament.
Ferrer will next face fellow Spaniard Nicolas Almagro, the fourth seed, who defeated Jeremy Chardy of France 7-6 (9-7) 6-3 in another quarter-final match.
Second-seeded Fabio Fognini of Italy and No.3 Tommy Robredo of Spain are also into the semi-finals, and they'll face each other on Saturday.
Fognini, who won the ATP event last week in Chile, advanced on Friday by defeating Pablo Andujar of Spain 6-4 6-3.
Robredo advanced against Robin Haase of the Netherlands. Robredo won the first set 6-1 and Haase retired with an injury after falling behind 2-0 in the second set.
World No.1 Rafael Nadal pulled out of the tournament with a back injury, but will play next week in the Rio Open.
