Roger Federer found the going tough

But he struggled in the second set as Robredo found his rhythm and forced Federer into numerous errors.

Robredo took the set on a tie-break, forcing a decider which proved a fiercely contested battle, with both players running down every ball out far and wide of the court.

Federer eventually sealed victory on his fourth match point after two hours on the hardcourt.

"I knew it would be a good fight - he runs and plays very well," said Federer of his Spanish opponent.

"I'm very satisfied I won this match because I gave away a lot of points."

In Thursday's other second-round matches, Romania's Andrei Pavel unleashed a near-flawless power game to dispatch German Rainer Schuettler 6-0 6-4.

Already through to the last eight are fourth seed Carlos Moya and fifth seed Jiri Novak.

Second round results (seeding in brackets):

J Melzer, Aus bt T Haas, Ger (1) 6-4 6-3
N Davydenko, Rus bt R Stepanek, Cze 6-1 5-7 7-5
R Federer, Swi (6) bt T Robredo, Spa 6-2 6-7 (5-7) 6-4
A Pavel, Rom bt R Schuettler, Ger 6-0 6-4
N Davydenko, Rus bt R Stepanek, Cze 6-1 5-7 7-5