Indian Wells, CA (SportsNetwork.com) - Defending champion Maria Sharapova was upset Monday, while Australian Open champ Li Na was an easy third-round winner at the $5.9 million BNP Paribas Open tennis event at Indian Wells Tennis Garden.

The fourth-seeded Sharapova, who won this event in 2013 and 2006, was stunned by 22-year old Italian Camila Giorgi. Giorgi, who had never faced Sharapova, took down the heavily favored Russian 6-3, 4-6, 7-5 on Day 6 in the California desert.

Seeking a third title in four events this season, the top-seeded Chinese star Li improved to 15-1 in 2014 by handling Czech Karolina Pliskova 6-3, 6-4.

The 32-year-old Li closed out the match with an ace, one of her 15 winners in a match in which the Chinese slugger piled up 28 unforced errors.

Li's fourth-round opponent will be surprising Canadian Aleksandra Wozniak, who took out 21st-seeded Russian Anastasia Pavlyuchenkova, 6-1, 6-7 (3-7), 6-0.

Eighth-seeded Czech Petra Kvitova defeated 27th-seeded Russian Svetlana Kuznetsova, 6-3, 2-6, 6-0. Kvitova improved to 3-0 lifetime against Kuznetsova, a runner-up at this event in 2007 and 2008.

American Sloane Stephens, the 17th seed, posted a 7-6 (7-3), 6-3 win over 11th-seeded Serbian Ana Ivanovic.

Meanwhile, 12th-seeded Slovak and Aussie Open runner-up Dominika Cibulkova bested 23rd-seeded Russian Ekaterina Makarova 6-4, 7-5; quality 20th-seeded Italian veteran Flavia Pennetta took out 16th-seeded former U.S. Open champ Sam Stosur of Australia, 6-4, 3-6, 6-1; and 24-year old Russian Alisa Kleybanova routed Spaniard Maria-Teresa Torro-Flor 6-1, 6-3.