Reigning Australian Open champion Jennifer Capriati suffered a shock first round defeat to world number 90 Marlene Weingartner of Germany.

Capriati, the winner in Melbourne for the last two years, earned the dubious honour of becoming the first ever reigning champion to lose in the first round.

"It took a few minutes to realise that I'd won," said Weingartner after her win.

"I've worked so hard for the last couple of months, I just went out there and went for it.

Weingartner is ranked only 90 in the world

"This is special. I have never played on centre court in a Grand Slam before," she added.

After a routine day of tennis in which there had been no real shocks, the match appeared to be following the script as Capriati led 6-2 3-0.

But the American completely lost her form and Weingartner took advantage to level the match on a second-set tie-break.

And the German was the dominant force in the third set as Capriati struggled to find any consistency, with double faults and unforced errors flowing from her racquet.

Capriati took a toilet break to compose herself when 2-1 down in the third set, but had to save two break points soon after she returned when serving at 2-3.

My eyes felt okay but the recovery time was not enough Jennifer Capriati

She faced three more in her next service game, and when Weingartner missed a simple forehand to break you sensed that the German may have blown her big chance.

But Weingartner held her nerve and made Capriati serve out at 4-5 to stay in the match.

Weingartner produced two stunning service returns to set up match point at 30-40 and Capriati netted a forehand to produce the first shock of the tournament.

Capriati laid the blame for her defeat on surgery she has recently had on her eyes.

"My eyes felt okay but I would have to say that the recovery time was not enough," she said.

"I didn't give myself enough time to prepare properly, and had I not been the defending champion I probably would not have showed up.

"I'm not trying to make excuses but I have to say that it affected my preparations for this tournament.

"Mentally and physically I just wasn't good enough," Capriati added.