Alex Corretja beat teenage compatriot Rafael Nadal in the biggest match of the opening day at the Pabellon de Crista.
The former world number two came through 6-2 3-6 6-4 against 17-year-old Nadal.
Corretja has suffered a miserable run of eight straight defeats since July.
But the 29-year-old Spaniard held his nerve in the deciding set, with Nadal missing a smash on Corretja's first match point.
In earlier matches, Nicolas Massu moved into round two with a comfortable 7-6 6-4 over Spain's Fernando Verdasco.
Massu won his second title of the year in Palermo last month before losing successive matches in Moscow and Vienna.
In the last 32, Massu will face former French Open champion Gustavo Kuerten.
South African Wayne Ferreira defeated Ivan Ljubicic of Croatia 7-6 7-6 before revealing he will retire at the end of 2004.
"The end of next year will be it for me," he said. "I have the goal of doing the Grand Slams and there's the possibility of getting back to the Olympics one more time.
"Then I think it's time to put my time and effort into my family."
Argentines Gaston Gaudio and Juan Ignacio Chela both edged through.
Gaudio beat Jarkko Nieminen of Finland 3-6 7-5 6-2, while Chela recovered for a 6-4 1-6 6-1 win over Alberto Martin.
The last match of the day saw Feliciano Lopez beat Argentina's Mariano Zabaleta 6-2 3-6 6-3.