The victory landed Monaco in the quarterfinals, where he could face top seed and defending champion Fernando Gonzalez.
Monaco had to withdraw before last year's final after hurting his ankle, allowing Gonzalez to win his third Movistar title.
Uruguay 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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