Petra Kvitova was the latest big-name casualty in the Qatar Open on Wednesday as teenager Jelena Ostapenko pulled off a third-round shock.
Australian Open champion Angelique Kerber was humbled by Zheng Saisai in the second round on Tuesday, while Simona Halep, Belinda Bencic and defending champion Lucie Safarova also crashed out.
Fifth seed Kvitova must have seen the early exits of such high quality rivals as a great opportunity to win her first title of the year, but world number 88 Ostapenko consigned the Czech to a 5-7 6-2 6-1 defeat which leaves only four of the 16 seeds still in the tournament.
Kvitova appeared to be on course for the quarter-finals when she recovered from being broken in the first game of the match to win a first set in which both players struggled on serve in Doha.
But the world number eight paid the price for being tentative, with the lively Ostapenko unleashing a powerful forehand to go a break up at 3-2 in the second set and breaking again before levelling the match all too easily.
Kvitova was up against it at 3-0 down in the decider and 18-year-old Latvian Ostapenko broke the two-time Wimbledon champion four times in total in the final set to take her place in the last eight.
Ostapenko will now face Zheng, who followed up her stunning win over Kerber by beating wildcard Eugenie Bouchard 7-6 (7-1) 6-1.
Bouchard had a set point leading 5-4 in the opener, but Zheng denied the Canadian and went on to dominate the tie-break before bossing a one-sided second set.
Caroline Wozniacki was another seed to bow out, as she was beaten 7-5 5-7 6-3 by qualifier Elena Vesnina - ranked 96 places below the former world number one.
Third seed Agnieszka Radwanska battled back from 4-1 down in the first set to beat Monica Niculescu 7-5 6-1 in Doha.
Garbine Muguruza, seeded four, marches on courtesy of a 6-2 7-5 victory over Timea Babos, while Carla Suarez Navarro saw off fellow-seed Timea Bacsinszky 6-2 6-2.
Roberta Vinci and Andrea Petkovic were also third-round winners on Wednesday.