Tszvetana Pironkova, who shocked Venus Williams 2-6, 6-0, 9-7 on Monday. (Reuters)

Melbourne: A defiant Venus Williams vowed to revive her faltering career Monday after being dumped from the Australian Open first round by little-known Bulgarian teenager Tszvetana Pironkova.

The former world No. 1 insisted her shock exit in a marathon three sets was a temporary setback that did not signal a terminal decline in her game.

Williams, who silenced her critics last year by reversing a form slump to win Wimbledon, dismissed suggestions she may struggle to once again dominate women’s tennis.

“There’s always going to be naysayers, you may be one of them, guess what, I don’t care,” she said.

The tournament No. 10 seed lost 6-2, 0-6, 7-9 in just under two-and-a-half hours in her worst Grand Slam performance since she was bundled out of the 2001 French Open at the first hurdle.

The 25-year-old American’s campaign appeared on track as she won the first set 6-2 in 36 minutes but the wheels fell off spectacularly in the second.

She made 14 unforced errors to Pironkova’s one and had her serve broken thrice.

In a nail-biting third set that lasted 86 minutes, Williams, whose left thigh was heavily strapped, broke the 18-year-old’s serve in the first game of the third, only to have the tenacious Bulgarian break back in the next.

Pironkova served for the match at 5-4 but Williams, who this week declared herself fully fit for the opening Grand Slam of the year, used her experience to stay afloat.

She dug deep, pounding herself on the head between points at times in the third set and mouthing the words “think, think”, but it was to no avail.

Williams said she “shot herself in the foot” by making 65 unforced errors to provide an opening for Pironkova. “She benefited from my largesse. If I had just a third less errors or ten less errors, I think this match would have been a different story.”

Williams admitted she struggled after the first set but put her poor form down to lack of match practice, saying she seldom played well so early in the season.

“I lost my form and I just feel like I could have been a little more positive but she played better,” she said. “I just started hitting the ball out, out, out. I just I don’t know, it just happens sometimes ... I just lost it.”

She denied her extracurricular activities, including studies and an interior design firm, had diluted her focus on tennis.

Pironkova, who jumped 201 spots in the rankings last year, rising from 295 to 94, said she was initially intimidated as Williams began her third set fightback but decided to go for broke. “I said ‘what the hell’ and started to play,” she told a cheering Melbourne Park crowd.

Despite winning five Grand Slams, Williams has never triumphed in Melbourne, with her 2003 loss in the final to sister Serena her best effort to date.

It was Pironkova’s debut appearance in Melbourne. She was crushed 6-1, 6-3 in her only previous meeting with Williams last year in Istanbul.