Swiss Stanislas Wawrinka stunned second seed David Ferrer 4-6, 6-1, 6-3 to reach the second round of the Zagreb indoor tournament on Tuesday.
Ferrer, ranked 10th in the world, broke in the third set to take a 3-2 lead but 20-year-old Wawrinka struck back and took advantage of several errors from the Spaniard to reach the last 16.
Third seed French Richard Gasquet easily overcame Davide Sanguinetti of Italy 6-3, 6-0, while fourth seed Radek Stepanek of the Czech Republic went through to the next round with a 6-3, 7-6 victory over compatriot Tomas Cakl.
A somewhat bigger effort was demanded of fifth seed Croat Mario Ancic, who beat Russian Dmitry Tusunov 6-3, 4-6, 6-4. Ancic broke Tusunov to take a 3-2 lead in the third set and kept his service until the end.
"I expected such a difficult match as I lost twice before from Tusunov. This time I played more aggressive tennis and it paid off," Ancic said.
Andreas Seppi of Italy defeated Israeli qualifier Noam Okun and will next face Croatian teenager Marin Cilic who disposed of Russian seventh seed Igor Andreev in the first round on Monday.
Top seed Ivan Ljubicic will face British teenager Andy Murray on Wednesday.
