BERLIN, May 17 (Xinhua) -- World number one Roger Federer ruled out a strong second set comeback from Argentine Juan Monaco to edge into the third round of the ATP Masters Series event in Hamburg on Wednesday.

Failing to rack up any title in the latest four tournaments for the first time since becoming world number one, the downcast Swiss mogul stuttered through Monaco 6-3, 2-6, 6-4.

"I had to fight to win and it was definitely a hard fought victory," said Federer. "The conditions were difficult but my opponent was good as well.

"Things were not always looking good today and I came out of a few difficult situations. It was not all straightforward."

Nadal, by contrast, was full of muscular confidence while beating his Spanish compatriot Oscar Hernandez 7-5, 6-1, taking eight games in a row from 4-5 in the first set. The French Open champion next plays Igor Andreev of Russia.

Two former world number one, Carlos Moya and Lleyton Hewitt, also came through the second round.