Melbourne, Australia (SportsNetwork.com) - Former champion Maria Sharapova and third seed Simona Halep notched wins, while former runner-up Ana Ivanovic was a stunning opening-round loser on Day 1 at the Australian Open.

The second-seeded former world No. 1 Sharapova eased past Croat Petra Martic 6-4, 6-1.

The reigning French Open champion titled here in 2008 and was an Aussie runner-up in 2007 and 2012.

Sharapova opened her 2015 season with a title in Brisbane two weeks ago. Her second-round opponent on Wednesday will be fellow Russian Alexandra Panova.

Last year's French Open runner-up to Sharapova, Halep, handled Italian Karin Knapp 6-3, 6-2 at Melbourne Park.

Halep opened her latest season with her ninth career title in Shenzhen, China, two weeks ago. She'll meet Aussie Jarmila Gajdosova on Day 3 this week.

Meanwhile, Czech Lucie Hradecka sent shockwaves by ousting fifth-seeded Ivanovic 1-6, 6-3, 6-2 at Rod Laver Arena.

The Serbian Ivanovic, who was the Aussie runner-up to Sharapova in 2008, suffered her earliest exit at a Grand Slam event since the French Open in 2011. She was a quarterfinalist in Melbourne last year.

"I think the whole match I didn't really feel like myself out there," Ivanovic said. "It was really tough for me to find a rhythm a little bit. In the third set, I really felt like she raised her level."

Hradecka, playing her first Grand Slam main draw since last year's Aussie Open, lost in qualifying at the other three majors in 2014. The doubles specialist entered the week ranked 142nd in singles play. She has 18 doubles titles, but none in singles.

"In the first set I was so nervous," Hradecka said. "I couldn't hit any balls in the court. When I went outside, I started to serve in the second set, I thought, 'Okay, it cannot be the worst. Let's play every point and let's see what will happen.'"

It's the earliest exit by a top-5 seed since 2003, when then No. 3 Jennifer Capriati was ousted by Marlene Weingartner.

Seventh-seeded Canadian star Eugenie Bouchard doused German Anna-Lena Friedsam 6-2, 6-4, while another upset saw Irina-Camelia Begu of Romania beat No. 9 seed Angelique Kerber of Germany, 6-4, 0-6, 6-1. Bouchard was the only woman to appear in three Grand Slam semifinals last year.

Bouchard's second-round opponent will be Dutchwoman Kiki Bertens.

In other action involving top-16 seeds, No. 10 Russian Ekaterina Makarova whipped Belgian An-Sophie Mestach 6-2, 6-2, No. 14 former Roland Garros runner-up Sara Errani drilled American Grace Min 6-1, 6-0 and Kazakhstan's Yaroslava Shvedova upended No. 16 Czech Lucie Safarova 6-4, 2-6, 8-6.

In other play involving seeds, German Carina Witthoeft took out No. 17 Spaniard Carla Suarez Navarro 6-3, 6-1; No. 21 Peng Shuai of China beat Germany's Tatjana Maria 6-4, 7-5; No. 22 Czech Karolina Pliskova defeated Russian Evgeniya Rodina 7-5, 6-1; Belgium's Yanina Wickmayer downed No. 23 Russian Anastasia Pavlyuchenkova 4-6, 6-3, 6-3; France's Caroline Garcia upset No. 27 Svetlana Kuznetsova of Russia 6-4, 6-2; France's Kristina Mladenovic doused No. 28 Sabine Lisicki of Germany 4-6, 6-4, 6-2; No. 31 Zarina Diyas of Kazakhstan overcame Pole Urszula Radwanska 3-6, 6-4, 6-2; and Germany's Julia Goerges vanquished No. 32 Belinda Bencic of Switzerland 6-2, 6-1.

Several other women moved on, including Americans Christina McHale and Bethanie Mattek-Sands, Puerto Rican Monica Puig and Italian veteran Roberta Vinci.

On Tuesday, top seed Serena Williams will meet Belgian Alison Van Uytvanck and fourth-seeded Wimbledon champ Petra Kvitova will face Dutchwoman Richel Hogenkamp. The reigning U.S. Open champion Williams owns 18 career Grand Slam titles, including a whopping five Aussie crowns.

Also slated for opening-round action on Day 2 are sixth-seeded former Wimbledon finalist Agnieszka Radwanska, eighth-seeded former No. 1 and 2014 U.S. Open runner-up Caroline Wozniacki, 11th-seeded 2014 Aussie Open runner-up Dominika Cibulkova, 18th-seeded former top-ranked star and former Aussie finalist Venus Williams, and unseeded two-time Aussie champ Victoria Azarenka, who will battle American Sloane Stephens.