World number one Roger Federer was back to his best on Tuesday to reach the last eight at the Sony Ericcson Open with a 7-6, 6-2 win over Jose Acasuso.
The Swiss top seed, who won the title in 2005 and 2006, made it through to his sixth Miami quarter-final on the back of an impressive service game against the Argentine world number 45.
Federer, who lost only 10 points on serve, will meet a familiar rival in Andy Roddick next. The American fought back from a set down to beat Julien Benneteau of France 4-6, 6-3, 6-2 in the fourth round.
World number two Rafael Nadal earned a 6-4, 6-4 win over Paul-Henri Mathieu of France to set up a quarter-final against American James Blake.
"It's always nice when you feel good from the beginning on your serve," Federer said. "It was key for me to serve well, especially in the beginning."
Federer showed no signs of struggling from the aftereffects of the glandular fever that took a toll on him at the start of the season -- he has yet to add a title this year to his haul of 53, which includes 12 grand slam trophies.
"You guys (the media) are always writing the stuff, and some people always talk a little bit too quickly," Federer said about his game going down a notch.
"For me, it was really a matter of getting back on tour, playing matches and hopefully playing well.
"Now I feel like I'm playing well. You can tell as well, I'm moving well and playing well and serving well."
There were no breaks in the first set and Federer squeezed through in the tiebreak 7-5 after winning the final two points.
Federer raced to a 4-0 lead in the second to unnerve Acasuso, who could only watch the world number one serve out the match to love starting with two aces.
Ninth seed Blake carved out a 6-3, 6-4 win over Czech Radek Stepanek.
"(He) doesn't play as conventional as a lot of the other guys," Blake said of his opponent. "He can move forward very well and defend very well. He's faster than he looks. He serves very well in big spots.
"So I feel like he can be tough."
In other men's fourth round matches, 10th-seeded Tomas Berdych of Czech Republic defeated Russia's Dmitry Tursunov 6-2 6-2.
Igor Andreev of Russia upset 15th seeded Guillermo Canas of Argentina 6-4, 7-6.
Tuesday's Results:
6-Andy Roddick (USA) beat Julien Benneteau (France) 4-6, 6-3, 6-2
Janko Tipsarevic (Serbia) beat 11-Mikhail Youzhny (Russia) 3-6, 6-0, 6-3
2-Rafael Nadal (Spain) beat 16-Paul-Henri Mathieu (France) 6-4, 6-4
1-Roger Federer (Switzerland) beat Jose Acasuso (Argentina) 7-6(5), 6-2
10-Tomas Berdych (Czech Republic) beat Dmitry Tursunov (Russia) 6-2, 6-2
31-Igor Andreev (Russia) beat 15-Guillermo Canas (Argentina) 6-4, 7-6(6)
9-James Blake (U.S.) beat 27-Radek Stepanek (Czech Republic) 6-3, 6-4
4-Nikolay Davydenko (Russia) beat Mario Ancic (Croatia) 4-6, 6-3, 7-5