Seeds are shaken by Sprem's flowering talent

When Karolina Sprem took to her chair on Centre Court last week she plucked two soft toys from her tennis bag and laid them down beside her. With her hair scraped back, and nervously straightening her dress, she looked like a gauche schoolgirl ready to sit an exam. Which, given she was about to face Venus Williams, was understandable. Just 102 minutes later and the young Croatian stepped from court a 7-6 7-6 victor after one of the most explosive and dramatic performances Wimbledon had seen in years. It was the earliest loss Williams had suffered in a major since 1997.

Amid the debris, and the furore over the extraordinary mistake made by umpire Ted Watts, when he wrongly awarded Sprem a point in the second set tie-break, and was later sacked for the error, commentators struggled for words. The Croatian Sensation, the Spreminator. It didn't seem to work.

Tracy Austin, the two-time US Open champion, simply and memorably, described Sprem as a "19-year-old flame-thrower". And it was Williams who was left scorched. The women's game may soon be in a similar state - such was the power and the intensity of her shots. New balls are called for every seven games. With Sprem around that may have to be revised which is all the more amazing given her comparatively slight 5ft 8in physique. "I love fast tennis, hard tennis and hitting the ball," says Sprem.

Austin went on to tip her as a new star who will continue the meteoric rise of the last two years when she went from 273 in the world, playing the lowest-ranked pro tournaments, with just $10,000 in prize-money to 57th in six months and now stands at 30th. During that rise she won 28 consecutive matches and four ITF tournaments. Scalps have been taken, twice beating Anna Smashnova-Pistolesi, defeating Jelena Dokic and Vera Zvonareva. She also pushed Williams to three-sets in Berlin last month - a contest John McEnroe said she should have won. Paola Suarez, one opponent, said: "I think she is going to be a great player. She is very strong mentally, really fast on the court and hits winners from both sides. She's really sweet too, so that's nice."

Despite the baseliner's aggression on court, the new Monica Seles some say, Sprem does indeed seem painfully shy of it and finds the circuit lonely. She lists her traits as "smiling a lot" but has struggled. "I don't have time to meet anyone," she confesses. "I'm travelling all the time, and I don't go out much." Though she is friends, through her coach, the former Croatian Davis Cup player Sasa Hirszon, with fellow Croatian Goran Ivanisevic - "he's my hero" - she has not met any of the other male tennis players. "Maybe when I'm playing more and more I'll go to a party or club in the evening," she says.

Even so, there isn't the money for much of a social life. Despite her promise Sprem (pronounced "Shprem") has, so far, not picked up so much as a free racket. Her parents, Gabro and Bozena, who live in the baroque town of Varazdin, fund her ambitions. "Sponsorship deals are the next level," she says. "Right now it's my dad who's paying for everything and it's not easy."

With her looks Sprem is well-placed to capitalise on the commercial side - the designer clothes and magazine covers. "Yeah, why not?" she says. Ivanisevic expects her to succeed. "Karolina Sprem could be the next star," he says. And despite her "niceness" there is a ruthless streak. American players such as Serena Williams and Andy Roddick, have commented harshly on her failure to tell the umpire that he had wrongly awarded her the point against Venus. "I'm an honest individual," says Serena. "So if I were in that situation, I know I would make the right choice."

A more reasoned perspective comes from Austin. "You don't want controversy associated with the biggest win of your career," she says. McEnroe agrees. "I blame her the least," he says. Venus, it shouldn't be forgotten, said Sprem deserved to win. The Croatian reacted angrily when it was suggested that the Williams' were on the wane. "Why you say this? Because I beat her?" she protested.

Her father, who runs a business making artificial flowers, has told her she will blossom into the top 10, and then No 1. "I say 'Come on dad'," says Sprem with a laugh before, revealing her self-belief, adding "but maybe one day". A glance at the bottom half of the women's draw is tantalising. Of the big guns only Lindsay Davenport remains. Against Williams, Sprem had nothing to lose. Now she has everything to gain.