TOP seed and world number one Rafael Nadal shrugged off the effects of a fever and a calamitous second set to battle past Lukas Lacko and book his place in the quarterfinals of the Exxonmobil Open in Doha.

Nadal looked to be heading for an early exit when he won just 11 points in the second set before fighting back to claim a 7-6 (7/3) 0-6 6-3 win over the Slovakian.

World number two and twice Doha champion Roger Federer was also required to work overtime for his lasteight place, before recording a 7-6 (7/5) 7-5 win over Swiss compatriot Marco Chiudinelli.

Third seed Jo-Wilfried Tsonga took just under one 75 minutes to defeat Ukrainian wild card Sergei Bubka and fifth seeded Latvian Ernests Gulbis was another winner, beating Croatian qualifier Antonio Veic 6-3 6-1.

Big-serving Ivo Karlovic hammered down 28 aces en route to knocking out German eighth seed Philipp Kohlschreiber 7-6 (7/5) 6-7 (4/7) 7-6 (7/2) after a marathon clash in which there were unsurprisingly no breaks of serve.

Sixth seeded Serbian Victor Troicki is next up for Federer after a 6-3 6-1 win over Russia’s Teymuraz Gabashvili, while seventh seed Guillermo Garcia-Lopez eased past Ukraine’s Ilya Marchenko 6-1 6-4.

n Andy Murray and Laura Robson lost their mixed doubles match against France as they were defeated 2-1 in the Hopman Cup in Perth. Robson had lost her singles match to Kristina Mladenovic 6-4 3-6 6-0 before Murray levelled the game with a 7-6 (7/3) 7-6 (7/5) win over Nicolas Mahut to set up a deciding match against the pair.

However, they were comprehensively beaten 6-4 6-2 in their Group B fixture.