Del Potro beat Lukasz Kubot 6-4, 6-2 by winning two-thirds of the points on serve and saving all four break points he faced. Kubot won a solid 61 percent of the points on serve but del Porto was able to cash in half of his six break-point chances.
Third-seeded Richard Gasquet was on the court just 55 minutes in routing Fabio Fognini. He lost 10 points over eight service games.
But Bobby Reynolds ousted second-seeded John Isner 3-6, 6-4, 6-3. Isner characteristically had 20 aces but uncharacteristically had his serve broken three times.
Also, Julien Benneteau took out fourth-seeded Feliciano Lopez 6-3, 6-4; Alex Bogomolov Jr. was a 7-6 (7-5), 6-4 winner over No. 5-seeded Viktor Troicki; and Jarkko Nieminen eliminated eighth-seeded Radek Stepanek 6-7 (7-5), 7-5, 1-6.
Del Potro goes against Baghdatis and Benneteau plays Bogomolov in the quarterfinals of the top half of the draw. Gasquet meets Istomin and Nieminen draws Reynolds in the other half.