Nadal dropped the first set but prevailed in the second despite five aces served up by Berlocq, and went on to win the match 3-6, 6-4, 6-4.
Nadal will meet another Argentine in Saturday's semifinal. Lucky-loser Martin Alund secured a match against Nadal by out-dueling Filippo Volandri, the defending champion of the tournament, 7-5, 7-6 (7-5).
David Nalbandian made the semis by topping three-time Brasil Open champion and No. 2 seed Nicolas Almagro 7-6 (7-5), 3-6, 7-6 (7-3). Almagro served 28 aces in the match but Nalbandian played a solid match with only one service break.
Nalbandian will face Simone Bolelli, who made the semis with a 6-4, 6-4 win over Albert Montanes of Spain.