Del Potro moves to quarters in Auckland

AUCKLAND, New Zealand, Jan. 14 (UPI) -- Juan Martin del Potro, the No. 1 seed, rallied Wednesday to down Ernests Gulbis in the second round of the Heineken Open in Auckland, New Zealand.

Del Potro, of Argentina, dropped the first set but came back strong to oust Latvia's Gulbis 3-6, 6-4, 6-2.

Second-seeded David Ferrer of Spain, the Auckland tourney winner in 2007, advanced with a 6-7 (3-7), 6-4, 6-4 win over France's Marc Gicquel.

Third-seeded Swede Robin Soderling beat American qualifier Bobby Reynolds 6-3, 4-6, 6-2.

Nicolas Almagro of Spain, seeded No. 4, eliminated Taipei's Yen-Hsun Lu 6-7 (4-7), 6-3, 6-2, fifth-seeded and defending champion Philipp Kohlschreiber of Germany topped Spaniard Juan Carlos Ferrero 6-4, 4-6, 7-6 (7-5) and sixth-seeded Sam Querrey of the United States beat qualifier Gilles Muller of Luxembourg 3-6, 6-3, 6-4.

In other matches, Serbian Viktor Troicki knocked out eighth-seeded Juan Monaco of Argentina 3-6, 6-4, 6-2 and American qualifier John Isner moved on with a 6-4, 6-7 (1-7), 7-6 (7-5) win over Robby Ginepri, also of the United States.