They finished their rivalry through the Latin American clay court swing at 2-2, although Robredo still leads 5-4 overall.
The No. 3 seed was on a 12-match winning streak after beating Acasuso in the semifinals en route to titles in Brazil and Argentina in the last two weeks.
On Thursday, Acasuso broke the Spaniard to clinch the first set without offering Robredo any break points and then raced through the second.
Seeking his first title in three years, the fifth-seeded Acasuso will play the winner of a late match between second-seeded Gael Monfils and Leonardo Mayer.
Nicolas Almagro continued his title defense with a 6-2, 7-6 (2), win over Daniel Gimeno-Traver and will meet Martin Vassallo Arguello for a place in Saturday's final.
Vassallo Arguello beat qualifier Dan Koellerer 6-3, 7-6 (6) to reach his first semifinals in two years.
Almagro had 14 aces, gave away only nine points in 10 service games, and gave Gimeno-Traver no break chances. Almagro took both of his break points in the first set then needed the tiebreaker to fend off 89th-ranked Gimeno-Traver.
In the women's draw, Flavia Pennetta maintained her bid for a sixth successive final in Acapulco by overcoming Petra Cetkovska 2-6, 6-3, 6-0 to improve her record in Acapulco to 27-4.
Second-seeded Pennetta, the champion in 2005 and 2008, set up a rematch of the 2004 final with Iveta Benesova, who beat Mathilde Johansson of France 6-1, 6-3.
Unseeded Barbora Zahlavova Strycova defeated Maret Ani 4-6, 7-5, 6-1 in 2 hours,43 minutes, and will play either top-seeded Venus Williams or Agnes Szavay.
Marcelo Delighted With First Real Madrid Goal
Almagro into Acapulco semifinals
