It was a day of shocks at the Indian Wells Masters tournament Monday as two of the biggest names in tennis suffered third round defeats.

Defending champion and world No. 1 Rafael Nadal was beaten in three sets by Ukraine's Alexandr Dolgopolov, while women's 2013 winner Maria Sharapova lost to Italian qualifier Camila Giorgi.

Spain's Nadal, bidding for his fourth triumph in California, had beaten 28th seed Dolgopolov in all of their previous five meetings, but the 13-time grand slam champion slipped to a 6-3 3-6 7-6 (7-5).

"I feel great, as after every win, of course," Dolgopolov, who will play Italy's Fabio Fognini in the fourth round, told the tournament's official website. "I beat the defending champion and the No. 1 in the world."

Nadal praised his opponent but admitted he wasn't feeling at his best during his two matches at the Indian Wells Tennis Garden.

"Since I started the competition here I didn't find the right feelings," said the 27-year-old. "It's true that I played against two opponents that probably didn't help me to get the rhythm in the tournament.

"But that's it. I was there. I saved tough situation the first day. Today I was close to save another one.

"But at the end, when you are on the limit, this thing happen. You can lose. I lost today. Congratulate him. He played I think better than me. That's it. Life continues. I'm going to keep working hard to try to be ready for Miami," added Nadal, who will take to the court for next week's Miami Masters.

Read: Federer, Murray advance at Indian Wells

In the women's draw, world No. 5 Sharapova became the latest big-name scalp to be taken by 79th-ranked Giorgi.

At Wimbledon 2012, Giorgi beat compatriot Flavia Panetta in the first round before eliminating former world No. 1 Caroline Wozniacki in the third round of last year's U.S. Open.

Giorgi's reward for her victory over Sharapova is a rematch with 20th seed Panetta, who beat Australia's Sam Stosur.

Sharapova was critical of her own performance after the first ever meeting between the two players.

"I did not play a good match at all, and I started very poorly," said the Russian. "(I had) Never played against her, but she's someone that doesn't give you much rhythm.

"She's quite aggressive, but some shots she hits incredible for a long period of time. Sometimes they go off a bit. But, if I'm speaking about my level, it was nowhere near where it should have been."