Pennetta, the No. 1 seed and No. 13 in the world rankings, struggled with her serve and was broken five times in the second-round match.
"It's okay. It's better to lose here than in Melbourne -- it's no big deal," Pennetta said of her preparation for next week's Australian Open.
She followed fourth-seeded Zheng Ji of China and seventh-seeded Alona Bondarenko of Ukraine out in the second round on a day when temperatures reached 99 degrees. Argentina's Gisela Dulko beat Zheng 6-3, 6-3 and Czech player Petra Kvitova had a 6-2, 6-1 win over Bondarenko.
The other seeded players gone before the end of the second round were Patty Schnyder (2) of Switzerland, Ana Chakvetadze (3) of Russia, Hungary's Agnes Szavay (5), Canadian Aleksandra Wozniak (6) and Tamarine Tanasugarn (8) of Thailand.
In other results Tuesday, Melinda Czink of Hungary advanced when Urszula Radwanska retired while trailing 4-2 in the first set, Iveta Benesova of the Czech Republic beat Italy's Mara Santangelo 6-3, 6-1 and Anastasia Pavlyuchenkova of Russia had a 6-4, 6-1 win over Spain's Carla Suarez-Navarro.
In the night match, Tvsetana Pironkova of Bulgaria raced to a 6-1, 6-2 win over Olga Govortsova of Belarus.