American Justin Gimelstob stunned Chile's Nicolas Massu 2-6, 7-6 (7/3), 6-4 to reach the quarter-finals of the Estoril Open on Wednesday.
Gimelstob, who travelled to Europe for only the second time in his career outside of three Roland Garros appearances, will now meet his doubles partner Albert Portas of Spain.
Portas booked his place with a knockout of French fourth seed
Gael Monfils 3-6, 7-6 (7/3), 6-4.
In women's play, the leading pair of seeds advanced.
Number one Italian Flavia Pennetta overcame Maret Ani of Estonia 6-4, 2-6, 6-2. The Italian is competing in Estoril after helping her nation to an upset Fed Cup win over France last month.
Second seed Gisela Dulko won an all-Argentine battle with ease
as she put out injury-hit 311th-ranked countrywoman Paola Suarez 6-2, 6-1.
