OEIRAS, Portugal (AP) - Former U.S. Open champion Juan del Potro cruised into the quarterfinals of the Estoril Open with a 6-1, 6-0 win over Rui Machado of Portugal on Thursday.

The top-seeded Argentine, who won at Flushing Meadow in 2009, looked to be only troubled in the third game of the first set when he saved two break points.

Del Potro will meet 2009 and 2010 champion Albert Montanes of Spain, who rallied past Bobby Reynolds of the United States 4-6, 6-4, 6-3.

Joao Sousa of Portugal advanced after fifth-seeded Denis Istomin of Uzbekistan withdrew when trailing 3-6, 6-3, 4-2.

Fourth-seeded Albert Ramos topped Bjorn Phau 7-5, 6-0.

In the women's event, top-seeded Roberta Vinci of Italy reached the semifinals by beating Nadia Petrova of Russia 6-2, 1-6, 6-4. The Italian rallied from 3-0 down in the final set.

Vinci will take on Kaia Kanepi of Estonia, who defeated Petra Cetkovska of the Czech Republic 6-3, 3-6, 6-3.

Carla Suarez Navarro defeated Silvia Soler-Espinosa 6-3, 6-3 in an all-Spanish match, and Karin Knapp defeated Galina Voskoboeva 7-6 (4), 2-6, 6-4.

SI Apps
We've Got Apps Too
Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.