He will now play James Blake, who ousted second seed Del Potro of Argentina.
In other second round matches, Grigor Dimitrov of Bulgaria defeated fourth seed Juan Ignacio Chela of Argentina 6-2, 5-7, 6-1 and Jarkko Nieminen of Finland eliminated third seed Stanislas Wawrinka of Switzerland in straight sets 6-3, 6-4.
Dimitrov will play Milos Raonic in the quarters and Nieminen will face Tobias Kamke of Germany.
Tobias Kamke (GER) – Sebastian Rieschick (GER) – 6-3, 6-1
Milos Raonic (CAN) – Philipp Petzschner (GER) – 6-3, 6-3