Australian seventh seed Lleyton Hewitt rallied to reach the quarter-finals of the 600,000-dollar ATP SAP Open on Thursday while Japanese eighth seed Kei Nishikori was eliminated.
Former world number one Hewitt ousted Argentina's Brian Dabul 3-6, 7-5, 6-3 in a second-round match. The two-time Grand Slam singles champion reached a last-eight matchup against another Argentine foe, Juan Martin Del Potro.
Del Potro, the 2009 US Open champion, has fallen from fourth to 484th in the rankings with a right wrist injury, but he beat Slovakian Lukas Lacko 6-1, 7-6 (7/1) to book a date with Hewitt, the 2001 US Open and 2002 Wimbledon champion.
Nishikori became the fourth seed to be sent packing, falling to 172nd-ranked US wild card Tim Smyczek 6-4, 3-6, 6-1.
Smyczek will face the winner of a later match between French second seed Gael Monfils, seeking his first title outside Europe, and American Robert Kendrick.
Uzbek fifth seed Denis Istomin advanced to the final eight as well, firing nine aces in eliminating American Michael Russell 7-6 (9/7), 7-6 (7/4).
Istomin put himself in the path of Spanish top seed and defending champion Fernando Verdasco, who was set to meet Croatian Ivo Karlovic in a later second-round match.