DOHA - Simona Halep again proved herself the most exciting new young star on the WTA circuit as she rode the storm which has blown away so many of the seeds at the Qatar Open. Halep, a 22-year-old Romanian who was voted WTA Tour newcomer of the year, needed less than an hour to overwhelm the fourth-seeded Sara Errani, and allowed one of the tour's gamest fighters only two games as she hurtled into the semi-finals.A highly effective first serve and strident flat hitting on the run built up Halep's impressive momentum, which earned the last seven games in succession and created a feeling that she will be climbing the top 10 standings she reached for the first time last month. "Actually I could not run very well because I have an injury," Halep said to a mixture of amazement and amusement after her 6-2, 6-0 success. "So I just wanted to be aggressive and finish the points as soon as I can."She succeeded so well in this that no-one uninitiated would have been aware she was carrying an Achilles strain. Halep may also have been motivated by the memory of a heavy defeat by the Italian in Miami last year. It means that 11 of the 15 seeds who started the tournament have failed to reach their allotted places. Earlier, the third-seeded former Wimbledon champion Petra Kvitova was ousted almost as quickly by Jelena Jankovic, whose recovery from a career-threatening plunge is continuing nicely.Purely in tennis terms, the result was not really a surprise, as the former world number one from Serbia had beaten the unpredictably talented Czech in their last meeting, late last year in Beijing. But the emphasis of the 6-1, 6-3 victory certainly was. Kvitova, who was not so long ago within two wins of becoming world number one herself was only briefly in the match at all.That happened when she began the second set with one of the only two service game she held throughout the match, and which took her to 2-0 and then 3-1. But that was the last game Kvitova won. "I am very consistent and that is what I am trying to do against the top players," said Jankovic. "You have to be at the top of your game if you want to beat players like this."Kvitova by contrast looked jaded. Her footwork was sometimes slow and her focus appeared to vary, as evidenced by a sudden spell of brilliance in the final game as her survival instincts kicked in, enabling her to save four match points. She was probably affected by a recent illness and two very hard three-setters - one against her friend Lucie Safarova, and the other against Venus Williams when she saved a match point."Everything hurts," said Kvitova. "No, really," she added as laughter followed. "I feel almost everything on my body. That's quite tough, but it's not like being injured. I tried, but, yeah, I wasn't really ready for it." For Jankovic the victory was a further indication that her climb, which has now reached world number eight, is continuing. Injuries caused her to fall to 34 in the rankings in 2012, since when she has rebuilt not only her body but her game. It has a more forceful service, and a greater emphasis on phases of early attack to leaven her skills at containment and counter-attack. Jankovic next has a semi-final with Angelique Kerber, the sixth-seeded German, whose progress came with embarrassing ease, 6-0, 6-1 against Petra Cetkowska.The Czech player seemed drained by the previous day's efforts over two and three-quarter hours in beating Li Na, the top-seeded Australian Open champion from China. The other semi-final will see Halep take on Agnieszka Radwanska, the second-seeded former Wimbledon finalist. The Pole was skilfully and cunningly impressive in a 6-2, 6-1 win over Yanina Wickmayer, who had treatment for a thigh strain, and looked very much the tournament favourite.