Petra Kvitova was the biggest casualty as five of the top 10 seeds crashed out in the third round of the WTA Dubai Tennis Championships on Wednesday.
The world number three won the tournament in 2013, but there will be no repeat this year after she was beaten 6-3 3-6 6-3 by Carla Suarez Navarro.
Second seed Kvitova struggled on serve as she was broken six times and double-faulted on 12 occasions in a match that lasted just over two hours.
Suarez Navarro surged into a 3-0 lead by breaking twice at the start of the match and, despite failing to hold in the following game, the Spaniard secured a third break to wrap up the set.
The second set followed a similar pattern, but this time it was Wimbledon champion Kvitova on top as she levelled the match by breaking three times.
That set up a tense decider, which went with serve until Suarez Navarro claimed a decisive break and served out despite the best efforts of Kvitova, who saved three match points.
Ana Ivanovic's week was also cut short after Karolina Pliskova fired down 13 aces in a surprise 6-2 4-6 6-4 victory over the world number six.
The clinical Pliskova, ranked 18 in the world, saved eight break points and broke the fourth seed six times to account for Ivanovic.
Agnieszka Radwanska also bowed out on Wednesday, as Garbine Muguruza consigned the fifth seed to a 6-4 6-2 loss to become the second Spaniard to claim an upset.
Top seed Simona Halep was not to be denied a place in the fourth round, though, as she overcame Tsvetana Pironkova 6-4 6-3 in the final match of the day.
Caroline Wozniacki had been hampered by injury and illness in her second-round victory over Sam Stosur on Tuesday, but the Dane marched on by outclassing Alize Cornet 6-4 6-0 a day later.
But Angelique Kerber, seeded seven, was swept aside in the final set in a 6-2 3-6 6-1 defeat versus Flavia Pennetta, and eighth seed Venus Williams lost 6-4 6-2 to Lucie Safarova.
Elsewhere in the draw, Ekaterina Makarova advanced at the expense of Zarina Diyas, prevailing 6-3 6-4.