Sydney, Australia ( - Juan Martin del Potro rallied past Nicolas Mahut to avoid becoming one of the many upset victims in second-round play at the Sydney International.

The top-seeded del Potro struggled to win just one game in his opening set of 2014, but roared back for a 1-6, 6-3, 6-4 triumph over the Frenchman on Wednesday.

Next up for the Argentine star in the quarterfinals will be Czech veteran Radek Stepanek, a 6-2, 7-6 (7-5) winner over Spain's Albert Ramos.

Fourth-seeded Dmitry Tursunov also shook off a sluggish start and advanced with a 3-6, 6-3, 6-3 victory over Lukas Rosol of the Czech Republic, but seeded players Jerzy Janowicz, Andreas Seppi, Julien Benneteau and Marin Cilic were all beaten on Wednesday.

Alexandr Dogolpolov of the Ukraine took out the second-seeded Janowicz with a 6-2, 6-2 rout and will next face defending Sydney winner Bernard Tomic, a 6-3, 4-6, 6-4 winner over Slovenian qualifier Blaz Kavcic.

Australian wild card Marinko Matosevic knocked out the third-seeded Seppi, 6-3, 6-4, and will next play Ukrainian qualifier Sergiy Stakhovsky, a 6-3, 6-2 winner over the sixth-seeded Benneteau.

Uzbekistan's Denis Istomin eliminated the seventh-seeded Cilic, 6-3, 6-4, to reach the quarterfinals against Tursunov.