Sao Paulo - Juan Monaco lost an opening-round match for the third time this season, falling to Simone Bolelli of Italy 7-5, 6-2 at the Brazil Open on Thursday.
The 15th-ranked Argentine had his service broken four times in the second-round loss at the indoor, clay-court tournament in South America's biggest city.
Monaco, who had a bye in the first round, lost his opening match at the Australian Open and last week in Vina del Mar, Chile.
The 80th-ranked Bolelli needed 1 hour, 16 minutes to defeat Monaco and advance to the quarter-finals in Brazil.
Top-seeded Rafael Nadal will play his first singles later on Thursday against Brazilian Joao Souza. The Spaniard withdrew from the doubles on Wednesday to preserve his injured left knee.
Results from the fourth day of the ATP Brazil Open on Thursday (x denotes seeding):
Carlos Berlocq (ARG) bt Albert Ramos (ESP x8) 7-6 (9/7), 6-4
Simone Bolelli (ITA) bt Juan Monaco (ARG x3) 7-5, 6-2
Nicolas Almagro (ESP x2) bt Paul Capdeville (CHI) 6-4, 6-7 (3/7), 6-2