Fernando Gonzalez had to save six break points in a tough tournament opener that took more than two hours.
The victory bought the Chilean star a quarterfinal with another Argentine, fifth-seeded Juan Monaco, the man he was supposed to meet in last year's final.
But Monaco had to withdraw before the final after spraining his ankle in the doubles final.
That allowed Gonzalez to win his third Movistar title.
Monaco set up their clash by beating Potito Starace of Italy 6-3, 6-3.
Uruguayan qualifier Pablo Cuevas upset third-seeded Alberto Montanes of Spain 7-6 (2), 6-4.
Cuevas, a semifinalist last year, said he wasn't intimidated by Montanes.
"I played well,'' he said. "It was difficult in the first set but I focused very well during the tiebreak and didn't make any mistakes. After that, the match was all for me.''
Cuevas will next play local wild card Paul Capdeville, who reached the quarterfinals of his hometown event for the first time in five attempts with a 6-4, 6-3 win over Daniel Gimeno-Traver of Spain.
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