Evergreen Japanese veteran Kimiko Date-Krumm came from behind to score an upset victory over Germany's Sabine Lisicki at the Stanford WTA tournament here Tuesday. (Click here for latest Tennis stories)
Date-Krumm, 44, who was forced to qualify for the main draw, looked to be heading to a rapid defeat after Lisicki whizzed through the first set, winning 6-1.
But the ageless Japanese favorite fought back brilliantly to clinch a second set tie-break before wrapping up the decider to seal a 1-6, 7-6 (7/4), 6-2 triumph.
Date-Krumm will now play Ajla Tomljanovic in the second round. Tomljanovic defeated Vitalia Diatchenko 3-6, 6-0, 6-0 to advance.
Elsewhere Tuesday, both seeded players in action advanced safely, with eighth-seeded Ukrainian Elina Svitolina beating compatriot Kateryna Bondarenko, 4-6, 6-4, 7-5.
German fifth seed Angelique Kerber, meanwhile, had little difficulty in dispatching Russia's Daria Gavrilova, winning 6-1, 6-3.
The field for this year's Stanford tournament was weakened on the eve of the event when world number one Serena Williams withdrew with an injury as she builds towards her tilt at a calendar Grand Slam at the US Open.
With Williams out, Denmark's Caroline Wozniacki is top seed.
Wozniacki, who received a bye in the first round, will play America's Varvara Lepchenko in her first match.
Lepchenko outlasted Mirjana Lucic-Baroni, 3-6, 6-2, 7-6(4) to advance to the second round.