World No 1 Roger Federer rolled over unseeded Jose Acasuso 7-6 (5), 6-2 in a fourth-round match at the $3.8 million ATP and WTA hardcourt tournament on Tuesday.

The top seeded Swiss star has not gone this deep into a season without winning a championship since 2000 - the last year he failed to win a title.

"It was key for me to serve well, especially in the beginning, and it was a good serving day today," said Federer. "I was very happy with it."

Winning in Miami would be nothing new to Federer, who claimed back-to-back titles at this men's and ladies' tournament from 2004-05.

The 26-year-old reached the fourth round here last year, but was upset by Guillermo Canas.

"Now I feel like I'm playing well," said Federer, who faces American Andy Roddick in the quarterfinals. "You can tell, as well, I'm moving well and playing well and serving well. That's what it comes down to for me.

"I had many matches where I came through in a close way, and that's what made me the best player for so long ... winning those big points over and over again."

Second seed Rafael Nadal, who lost to Federer in the 2005 final, also reached the quarterfinals on Tuesday by beating 15th-seeded Frenchman Paul-Henri Mathieu 6-4, 6-4.

The Spaniard owns a commanding 8-0 lead in the all-time series against Mathieu, who retired from their match at the Australian Open in January. Like Federer, Nadal has yet to win on tour this season.

Ninth-seeded American James Blake is through to the quarterfinals after claiming a 6-3, 6-4 win over No 27 Radek Stepanek.

Roddick will join his compatriot in the last eight. Roddick struggled in the first set before rallying to beat unseeded Frenchman Julien Benneteau 4-6, 6-3, 6-2.

Roddick, who announced his engagement to swimsuit model Brooklyn Decker, won here in 2004 and is making his ninth-straight appearance.

Roddick is facing a monumental task as he has lost 15 of his career 16 meetings with Federer.