PHOTOS: Shocking early exits at Australian Open...

Rediff.com presents the early surprises at the year's first Grand Slam.

Petkovic dumps Kvitova out after epic match

Petra Kvitova

IMAGE: A disappointed Petra Kvitova walks off the court after losing her first round match against Andrea Petkovic. Photographs: Cameron Spencer/Getty Images

Two-time Wimbledon champion Petra Kvitova's return to the Australian Open a year after being attacked by an intruder at her home ended in disappointment with a epic 6-3, 4-6, 10-8 first-round loss to German Andrea Petkovic on Tuesday.

A former quarter-finalist at Melbourne Park, Kvitova missed last year's event as she recovered from surgery to her left hand which was injured by a knife-wielding assailant weeks before the tournament.

The crowd groaned in disappointment, while Petkovic roared in triumph and Czech Kvitova walked off to warm applause in the twilight.

Raonic slumps to early exit at Melbourne Park

Milos Raonic

IMAGE: Milos Raonic of Canada serves to Lukas Lacko of Slovakia. Photograph: Edgar Su/Reuters.

Former world number three Milos Raonic said he would go back to the drawing board after Lukas Lacko sent him tumbling out in the first round of the Australian Open, on Tuesday, the Canadian's earliest Grand Slam exit since the 2011 French Open.

On the comeback trail after a 2017 season disrupted by injury, Raonic looked off the pace as he was picked apart 6-7(5), 7-5, 6-4, 7-6(4) by the 86th-ranked Slovak on showcourt two.

"I was not prepared for this situation so I will take a whole new review," Raonic told reporters.

"I was hoping I would be able to work my way in (to the tournament) but that's not the case."

A miserable day session for America saw US Open champion Sloane Stephens, seven-time Grand Slam winner Venus Williams, men's 16th seed John Isner and eighth seed Jack Sock, the highest ranked US player in the men's draw, all exit the tournament.

Venus Williams

IMAGE: A disappointed Venus Williams of the United States walks off the court after losing her first round match against Belinda Bencic of Switzerland on Day 1 of the Australian Open. Photograph: Cameron Spencer/Getty Images.

Belinda Bencic sent an early shockwave through the Australian Open by dumping last year’s finalist Venus Williams out of the first round with an impressive 6-3, 7-5 win on Monday.

The 20-year-old Swiss played the 37-year-old American great to perfection, soaking up the fifth seed’s firepower and attacking her wavering serve with abandon under the roof at Rod Laver Arena.

Stephens tumbles out

Sloane Stephens

IMAGE: Sloane Stephens stretches for a shot. Photograph: Issei Kato/Reuters.

The stark contrast in form between last year's two first-time Grand Slam champions continued as Sloane Stephens was bundled out in the first round.

American Stephens enjoyed a fairytale run to win the US Open last year ranked 83rd in the world but has not won a match since -- a run that continued with a 2-6, 7-6(2), 6-2 defeat by China's Zhang Shuai on Margaret Court Arena.

Edmund out-guns Anderson for first round shock

Kyle Edmund

IMAGE: Kyle Edmund and Kevin Anderson shake hands after Edmund won their match. Photograph: Edgar Su /Reuters.

Britain's Kyle Edmund outfought Kevin Anderson over nearly five hours to send the 11th seed tumbling out of the Australian Open 6-7(4), 6-3, 3-6, 6-3, 6-4 in the first round.

The world number 49 twice needed to come from a set down to force a deciding fifth set, where again he battled back from a break down to set up a second round clash with Uzbek Denis Istomin.

Vandeweghe sent packing by Timea Babos

Coco Vanderweghe

IMAGE: Coco Vandeweghe of the United States shows her frustration. Photograph: Ryan Pierse/Getty Images.

Coco Vandeweghe was given two code violations during her stormy 7-6(4), 6-2 defeat by Hungarian Timea Babos at the Hisense Arena.

Vandeweghe became the third of four American women who made the semi-finals at last year's US Open to fall at the first hurdle at Melbourne Park on Monday.